I'm in the mood today to write my own functions. try this
Function FindLast(ShortString, LongString) As Integer
Shortlength = Len(ShortString)
LongLength = Len(LongString)
FindLast = 0
If (Shortlength <= LongLength) Then
StringPosition = LongLength - Shortlength + 1
For i = StringPosition To 1 Step -1
If (StrComp(ShortString, Left(Mid(LongString, i, Shortlength),
Shortlength)) = 0) Then
FindLast = i
Exit For
End If
Next i
End If
End Function