PostFiles.bas

Sub PostFiles()
  ' Note: Add reference to Microsoft Scripting Runtime
  '       (Tools > References)

  ' References:
  ' http://www.xl-central.com/list-files-fso.html
  ' http://stackoverflow.com/a/20391100/1240745
  
  Dim FSO As New FileSystemObject
  Dim XmlFolder As Folder
  Dim XmlFile As File
  Dim XmlStream As TextStream
  
  Set XmlFolder = FSO.GetFolder("C:\xml\")
  If XmlFolder.Files.Count = 0 Then
    ' No files found...
    Exit Sub
  End If

  ' Setup Client and most of Request outside of loop
  Dim Client As New WebClient
  Dim Request As New WebRequest
  Dim Response As WebResponse
  
  Client.BaseUrl = "https://webservice.../"
  Request.Resource = "xml/{filename}"
  
  For Each XmlFile In XmlFolder.Files
    Request.AddUrlSegment "filename", XmlFile.Name

    XmlTextStream = XmlFile.OpenAsTextStream(1)
    Request.Body = XmlTextStream.ReadAll
    XmlTextStream.Close
    
    Set Response = Client.Execute(Request)
    
    ' Check Immediate Window (ctrl + g)
    Debug.Print XmlFile.Name & " -> " & Response.StatusCode & ": " & Response.Content
  Next XmlFile
End Sub