Actually, in Monty's case, since the function is only throwing up a
msgbox, it works fine, he just needs to get his formulas correct:

D1: =IF(DAYS360(B1,C1)15,PromptPayment(),DAYS360(B1,C 1)

or

D1: =IF((C1-B1)15,PromptPayment(),C1-B1)


In article ,
"Otto Moehrbach" wrote:

A formula in a cell can only return a value to that cell, it cannot
trigger a macro or a function to run.