Hi. I have been trying to get my head around some formulas and it has been
driving me crazy (yea, one of them beginners, me!!)

Basically, I need to add numbers from a range of cells, but do not want the
result to exceed a certain value. For example, I want the sum of cells A1,
A2, A4, B5 & B6 to be displayed in cell C15, however, if the sum is more than
128, it should pop up with an error box asking the user to re-evaluate the
numbers entered in the cells to be calculated.

I need to use this to send to my clients to fill in the numbers and send
back to me, so I also want to know if it is possible to protect the formulas
entered, even if they save it as another file.

Any help really, really appreciated.

Cheers
Ken