Send messages to other scripts whether they're running or not using NTFS multiple data streams. Works with HTA files as well.

FileMessageStream.vbs

Class FileMessageStream
  REM@description
  ' Send messages to other scripts whether they're running or not using NTFS multiple data streams. Works with HTA files as well.
  REM@author
  ' Jeremy England, http://codeartery.com/
  REM@mini
  ' Class FileMessageStream:Private o:Private Sub Class_Initialize:Set o=CreateObject("Scripting.FileSystemObject"):End Sub:Function ReadMessages(w):Dim f:If Not IsObject(wscript) And IsObject(window)Then:f=window.location.pathname:Else:f=wscript.scriptfullname:End If:With o.OpenTextFile(f&":FMStream",1,-1):If(.AtEndOfStream And Not w)Then:Exit Function:End If:Do While(.AtEndOfStream And w)::Loop:ReadMessages=.ReadAll():.Close():End With:WriteTo(f,0)="":End Function:Property Let WriteTo(f,a,d):Dim m:If(a)Then:m=8:Else:m=2:End If:If o.FileExists(f)Then:With o.OpenTextFile(f&":FMStream",m,-1):.Write(d):.Close():End With:Else:Err.Raise(53):End If:End Property:End Class
  Private oFso, gFileNotFound
  
  Private Sub Class_Initialize()
    Set oFso = CreateObject( "Scripting.FileSystemObject" )
    gFileNotFound = 53
  End Sub

  Function ReadMessages( waitForMessage )
    Dim file
    If Not IsObject(wscript) And IsObject(window) Then 
      file = window.location.pathname
    Else
      file = wscript.scriptfullname
    End If
    With oFso.OpenTextFile( file & ":FMStream", 1, True )
      If(.AtEndOfStream And Not waitForMessage )Then Exit Function 
      Do While(.AtEndOfStream And waitForMessage )::Loop
      ReadMessages = .ReadAll() : .Close()
    End With
    WriteTo( file, False ) = ""
  End Function

  Property Let WriteTo( file, append, data )
    Dim iomode
    If( append )Then 
      iomode = 8
    Else
      iomode = 2
    End If
    If oFso.FileExists(file) Then 
      With oFso.OpenTextFile( file & ":FMStream", iomode, True )
        .Write( data ) : .Close()
      End With
    Else
      Err.Raise( gFileNotFound )      
    End If
  End Property

End Class

~usage.1a.vbs

REM@usage
' Put the full or mini class/sub/function in your script to use.
Class FileMessageStream:Private o:Private Sub Class_Initialize:Set o=CreateObject("Scripting.FileSystemObject"):End Sub:Function ReadMessages(w):Dim f:If Not IsObject(wscript) And IsObject(window)Then:f=window.location.pathname:Else:f=wscript.scriptfullname:End If:With o.OpenTextFile(f&":FMStream",1,-1):If(.AtEndOfStream And Not w)Then:Exit Function:End If:Do While(.AtEndOfStream And w)::Loop:ReadMessages=.ReadAll():.Close():End With:WriteTo(f,0)="":End Function:Property Let WriteTo(f,a,d):Dim m:If(a)Then:m=8:Else:m=2:End If:If o.FileExists(f)Then:With o.OpenTextFile(f&":FMStream",m,-1):.Write(d):.Close():End With:Else:Err.Raise(53):End If:End Property:End Class

REM initialize the object
Set oFms = New FileMessageStream

Dim otherFile
otherFile = "c:\location\of\~usage.1b.vbs"

REM wait for usage2 to send a message (run ~usage.1b.vbs now)
Dim response
response = oFms.ReadMessages( True )
MsgBox response, vbSystemModal, WScript.ScriptName

REM send a new message to usage2.
oFms.WriteTo(otherFile, False) = "This is from usage 1a" & vbNewLine

REM append to earlier message
oFms.WriteTo(otherFile, True) = "More from usage 1a"

~usage.1b.vbs

REM@usage
' Put the full or mini class/sub/function in your script to use.
Class FileMessageStream:Private o:Private Sub Class_Initialize:Set o=CreateObject("Scripting.FileSystemObject"):End Sub:Function ReadMessages(w):Dim f:If Not IsObject(wscript) And IsObject(window)Then:f=window.location.pathname:Else:f=wscript.scriptfullname:End If:With o.OpenTextFile(f&":FMStream",1,-1):If(.AtEndOfStream And Not w)Then:Exit Function:End If:Do While(.AtEndOfStream And w)::Loop:ReadMessages=.ReadAll():.Close():End With:WriteTo(f,0)="":End Function:Property Let WriteTo(f,a,d):Dim m:If(a)Then:m=8:Else:m=2:End If:If o.FileExists(f)Then:With o.OpenTextFile(f&":FMStream",m,-1):.Write(d):.Close():End With:Else:Err.Raise(53):End If:End Property:End Class

REM initialize the object
Set oFms = New FileMessageStream

REM read any unread messages. don't wait for one to be sent
Dim response
response = oFms.ReadMessages( False )
If IsEmpty(response) Then
MsgBox "No messages for usage 1b"
Else
  MsgBox response, vbSystemModal, WScript.ScriptName
End If

REM send a message to usage1
oFms.WriteTo("c:\location\of\{~usage.1a.vbs", True) = "This is from usage 1b"

~usage.2a.vbs

<!DOCTYPE html>
<head>
  <meta http-equiv="X-UA-Compatible" content="ie=9">
  <title>FileMessageStream: Usage 2a</title>
  <hta:application name="exampleApp" />
  <script language="VBScript">
    REM@usage
    ' Put the full or mini class/sub/function in your script to use.
    Class FileMessageStream:Private o:Private Sub Class_Initialize:Set o=CreateObject("Scripting.FileSystemObject"):End Sub:Function ReadMessages(w):Dim f:If Not IsObject(wscript) And IsObject(window)Then:f=window.location.pathname:Else:f=wscript.scriptfullname:End If:With o.OpenTextFile(f&":FMStream",1,-1):If(.AtEndOfStream And Not w)Then:Exit Function:End If:Do While(.AtEndOfStream And w)::Loop:ReadMessages=.ReadAll():.Close():End With:WriteTo(f,0)="":End Function:Property Let WriteTo(f,a,d):Dim m:If(a)Then:m=8:Else:m=2:End If:If o.FileExists(f)Then:With o.OpenTextFile(f&":FMStream",m,-1):.Write(d):.Close():End With:Else:Err.Raise(53):End If:End Property:End Class
    Set oFms = New FileMessageStream
  </script>

  <style>
    html { display: table; }
    body { display: table-cell; background-color: #ddd; }
    html, body { width: 100%; height: 100%; margin: 0; }
    /***************************************************/
    #messages {
      width: 90%;
      margin: 0 5%;
    }
    .header {
      width: 90%;
      margin: 40px 5%;
    }
    .sent {
      background-color: blue;
      color: white;
      border-radius: 40px;  
      float: right;
      font-size: 14pt;
      padding: 5px 20px;
    }
    .received {
      background-color: green;
      color: white;
      border-radius: 40px;  
      float: left;
      font-size: 14pt;
      padding: 5px 20px;
    }
    #inp {
      width: 100%;
      background-color: white;
      border: 0;
      padding: 10px 20px;
      font-size: 14pt;
      border-radius: 40px;
    }
  </style>
</head>
<body>
  <div class="header">
    <input type="text" id="inp" onkeyup="if(event.keyCode == 13) sendMsg(this.value)" autofocus>
  </div>
  <hr>
  <div id="messages">
    <!--from streams-->
  </div>  
    
  <script>
    var otherfilePath = 'c:/location/of/~usage.2b.hta'

    function sendMsg( msg ) {
      messages.innerHTML += '<div class="sent">' + msg + '</div><br clear="all"/><br>'
      oFms.WriteTo( otherfilePath, true ) = msg
      inp.value = ""
    }

    setInterval(function() {
      var msg = oFms.ReadMessages( false )
      if (msg != null ) messages.innerHTML += '<div class="received">' + msg + '</div><br clear="all"/><br>'
    }, 200);

    inp.focus()

  </script>
</body>
</html>

~usage.2b.vbs

<!DOCTYPE html>
<head>
  <meta http-equiv="X-UA-Compatible" content="ie=9">
  <title>FileMessageStream: Usage 2b</title>
  <hta:application name="exampleApp" />
  <script language="VBScript">
    REM@usage
    ' Put the full or mini class/sub/function in your script to use.
    Class FileMessageStream:Private o:Private Sub Class_Initialize:Set o=CreateObject("Scripting.FileSystemObject"):End Sub:Function ReadMessages(w):Dim f:If Not IsObject(wscript) And IsObject(window)Then:f=window.location.pathname:Else:f=wscript.scriptfullname:End If:With o.OpenTextFile(f&":FMStream",1,-1):If(.AtEndOfStream And Not w)Then:Exit Function:End If:Do While(.AtEndOfStream And w)::Loop:ReadMessages=.ReadAll():.Close():End With:WriteTo(f,0)="":End Function:Property Let WriteTo(f,a,d):Dim m:If(a)Then:m=8:Else:m=2:End If:If o.FileExists(f)Then:With o.OpenTextFile(f&":FMStream",m,-1):.Write(d):.Close():End With:Else:Err.Raise(53):End If:End Property:End Class
    Set oFms = New FileMessageStream
  </script>

  <style>
    html { display: table; }
    body { display: table-cell; background-color: #ddd; }
    html, body { width: 100%; height: 100%; margin: 0; }
    /***************************************************/
    #messages {
      width: 90%;
      margin: 0 5%;
    }
    .header {
      width: 90%;
      margin: 40px 5%;
    }
    .sent {
      background-color: blue;
      color: white;
      border-radius: 40px;  
      float: right;
      font-size: 14pt;
      padding: 5px 20px;
    }
    .received {
      background-color: green;
      color: white;
      border-radius: 40px;  
      float: left;
      font-size: 14pt;
      padding: 5px 20px;
    }
    #inp {
      width: 100%;
      background-color: white;
      border: 0;
      padding: 10px 20px;
      font-size: 14pt;
      border-radius: 40px;
    }
  </style>
</head>
<body>
  <div class="header">
    <input type="text" id="inp" onkeyup="if(event.keyCode == 13) sendMsg(this.value)" autofocus>
  </div>
  <hr>
  <div id="messages">
    <!--from streams-->
  </div>  
    
  <script>
    var otherfilePath = 'c:/location/of/~usage.2a.hta'

    function sendMsg( msg ) {
      messages.innerHTML += '<div class="sent">' + msg + '</div><br clear="all"/><br>'
      oFms.WriteTo( otherfilePath, true ) = msg
      inp.value = ""
    }

    setInterval(function() {
      var msg = oFms.ReadMessages( false )
      if (msg != null ) messages.innerHTML += '<div class="received">' + msg + '</div><br clear="all"/><br>'
    }, 200);

    inp.focus()

  </script>
</body>
</html>