First of all press F1 in VBA and lookup Choose
Code:
        For i = 13 To 24
            If Me("Checkbox" & i) Then Sheets("Schedule").Range(Choose(i-12, "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
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