I have this backup function and I want to include code to
ensure that the backup only occurs once for the end of
the month. If someone tries to do it again they get a
message saying that it has already been backed up today?

Dim awb As Workbook, BackupFileName As String, i As
Integer, OK As Boolean
If TypeName(ActiveWorkbook) = "Nothing" Then Exit Sub
Set awb = ActiveWorkbook
If awb.Path = "" Then
Application.Dialogs(xlDialogSaveAs).Show
Else
BackupFileName = awb.FullName
i = 0
While InStr(i + 1, BackupFileName, ".") 0
i = InStr(i + 1, BackupFileName, ".")
Wend
If i 0 Then BackupFileName = Left
(BackupFileName, i - 1)
'BackupFileName = BackupFileName & ".bak"
OK = False
On Error GoTo NotAbleToSave
With awb
Application.StatusBar = "Saving this
workbook..."
.Save
Application.StatusBar = "Saving this workbook
backup..."

ThisWorkbook.SaveCopyAs Left
(ThisWorkbook.FullName, Len( _
ThisWorkbook.FullName) - 4) & Format
(Date, "_yyyy_mm_dd") & ".bak"



'.SaveCopyAs BackupFileName
OK = True
End With
End If
NotAbleToSave:
Set awb = Nothing
Application.StatusBar = False
If Not OK Then
MsgBox "Backup Copy Not Saved!", vbExclamation,
ThisWorkbook.Name

Else
MsgBox "Backup was successful!", vbInformation,
ThisWorkbook.Name

End If