Capture Future Changes To The Sheet As The Same Saved Name But To Add And Extention Like (-Rev1).

I am using the following save as function on a template to save it as a workbook:

Sub SaveFileAsDate()
Dim WSName As String, CName As String, Directory As String, savename As String
WSName = "TMG Work Order"
CName = "C4"
Directory = "Maintenance Service Agreements"
savename = Sheets(WSName). Range(CName).Text & Sheets(WSName).Range("F3").Text & Sheets(WSName).Range("K4").Text & Sheets(WSName).Range("K8").Text
If Directory = "" Then Directory = CurDir & ""

On Error Goto errorsub:
ActiveWorkbook.SaveAs Filename:=Directory & savename & ".xls"
Exit Sub

errorsub:
Beep
MsgBox " Changes not saved!", vbExclamation, Title:=savename & ".xls"
End Sub

It works fine but I need to be able to capture future changes to the sheet as the same saved name but to add and extention like (-Rev1). Once it has been saved as -Rev1, each additional time it saves, the -Rev number would increase. I searched the forums but didn't find an exact match.