I'm using Crystal Reports 11. I have a formula in which I keep getting the Error Message: "A string is required here". My code is below.

Code:
Dim dy, mo as string

mo = month(CDate({tblTimeSheetDetail.monDate}))
dy = day(CDate({tblTimeSheetDetail.monDate}))

formula = mo & "/" & dy
The error is occurring on the hightlighted line but will probably occur on the next line as well.

Thanks,