OK thanks for the info, indeed it works now, but what if I had j instead of i, why would this also crash?

Code:
 For j = 13 To 24
            If Me("Checkbox" & j) Then Sheets("Schedule").Range(Choose(j, "sep_pay", "oct_pay", "nov_pay", "dec_pay", _
                "jan_pay", "feb_pay", "mar_pay", "apr_pay", "may_pay", "jun_pay", "jul_pay", "aug_pay")).ClearContents
        Next
Guess I 'd better check F1 first but thanx anyway for your help both times.