Function myReplaceFileText(myFilePathInput As String, myFilePathOutput As String, myReplaceString As String, myString As String)
     
    Dim myFileString As String
     
    Open "C:\folder\file.txt" For Input As #1
    myFileString = Input(LOF(1), 1)
    Close #1
     
    myFileString = Replace(myFileString, myReplaceString, myString, Compare:=vbTextCompare)
    
    Open myFilePathOutput For Output As #2
    Print #2, myFileString
    Close
End Function
Sub Test()
     
    Dim myFilePathInput As String
    Dim myFilePathOutput As String
    Dim myReplaceString As String
    Dim myString As String
     
    myFilePathInput = "C:\folder\file.txt"
    myFilePathOutput = "C:\folder\file.txt"
    myReplaceString = ","
    myString = ""
     
    Call myReplaceFileText(myFilePathInput, myFilePathOutput, myReplaceString, myString)
     
End Sub