Yes, you could use a worksheet_change event triggered by input into the 2nd
cell.

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Don Guillett
SalesAid Software

"Monty" wrote in message
...
Hi all,

At present i have to cells with dates input by staff, in the third cell
the
number of days are calculated. can i run a formula to bring up a message
box
to say issue prompt payment letter if the days calculated are over 15.
thanks