Near as I can tell the procedures described he

http://www.mcgimpsey.com/excel/timestamp.html

are for determing when the data entered in the cell changes, but does not
detect whether a formula returns a different result. For example it
correctly indicates when a value is entered into a cell, but for the
"=sum(a1:10)" value entered in B1, the Time stamp does not trigger when new
values are entered anywhere in A1:a10 that changes the sum.

Does the description make sense?

Any help/points for triggering the time stamp procedure in cell b1 when any
of the values in a1:a10 change the sum value in b1?

Thanks,
M John