Append A Prefix String to Current Filename and Overwrite

Hi,

I am trying to add a Prefix string (with if condition) to the current filename and overwrite at the same location as the current file. A certain Prefix is appended to the current filename if the filename contains a partciular string such as 0915 or 1215, etc, then the file name is overwritten and saved and then moved to next file in the directory.

However, I am not getting any result and its not working, may be its having trouble with Prefix declaration, but I can't figure it out as per my very limited excel vba knowledge. How can I make it work? For which reason it isn't working, this code? The vba code is pasted below:

Sub ChangeFilename()
Dim mybook As Workbook
Dim MyPath As String, FilesInPath As String
Dim MyFiles() As String, Prefix As Variant
Dim MyFile As String, FNum As Long, fMame As String


MyPath = "C:\data2\one"

    ' Add a slash at the end of path if needed.
    If Right(MyPath, 1) <> "\" Then
        MyPath = MyPath & "\"
    End If

    ' If there are no Excel files in the folder, exit.
    FilesInPath = Dir(MyPath & "*.xlsx*")
    If FilesInPath = "" Then
        MsgBox "No files found"
        Exit Sub
    End If

    ' Fill in the myFiles array with the list of Excel files in
    ' the search folder.
    FNum = 0
    Do While FilesInPath <> ""
        FNum = FNum + 1
        ReDim Preserve MyFiles(1 To FNum)
        MyFiles(FNum) = FilesInPath
        FilesInPath = Dir()
    Loop

    
    If FNum > 0 Then
        For FNum = LBound(MyFiles) To UBound(MyFiles)
    Set mybook = Nothing
            On Error Resume Next
            Set mybook = Workbooks.Open(MyPath & MyFiles(FNum))
            On Error GoTo 0
            
    sFileName = mybook.FullName
    
    If InStr(1, sFileName, "0915", vbTextCompare) > 0 Then
    Prefix = "SRJ1"
    
    ElseIf InStr(1, sFileName, "1215", vbTextCompare) > 0 Then
    Prefix = "SRJ2"
    
    ElseIf InStr(1, sFileName, "1315", vbTextCompare) > 0 Then
    Prefix = "SRJ3"
    
    ElseIf InStr(1, sFileName, "1515", vbTextCompare) > 0 Then
    Prefix = "SRJ4"
    
    ElseIf InStr(1, sFileName, "1715", vbTextCompare) > 0 Then
    Prefix = "SRJ5"
    
    ElseIf InStr(1, sFileName, "2315", vbTextCompare) > 0 Then
    Prefix = "SRJ6"
    
    ElseIf InStr(1, sFileName, "0900", vbTextCompare) > 0 Then
    Prefix = "SRJ7"
    
    ElseIf InStr(1, sFileName, "1200", vbTextCompare) > 0 Then
    Prefix = "SRJ8"
    
    ElseIf InStr(1, sFileName, "1800", vbTextCompare) > 0 Then
    Prefix = "SRJ9"
    
    End If
    mybook.Activate
    fName = Prefix & sFileName & ".xlsx"
   ActiveWorkbook.SaveAs ActiveWorkbook.Path & fName
    mybook.Close
    
    Next FNum
    End If
    
End Sub

Thanks for your help.

Sanjeev.