test.bas

Sub Testing()
    
    MsgBox "Is file open?: " & IsFileOpen("<File Path>")

End Sub


Public Function IsFileOpen(ByVal File_Path As String) As Boolean
    
    Dim fileNum As Long, errNumber As Long
    
    On Error Resume Next
    fileNum = FreeFile()
        
    Open File_Path For Input Lock Read As #fileNum
    Close fileNum
    errNumber = Err
    
    On Error GoTo 0
    
    Select Case errNumber
    
        Case 0
            IsFileOpen = False
        
        Case 70
            IsFileOpen = True
        
        Case Else
            Error errNumber
            
    End Select

End Function