Conditional mandatory field ?

[peter.hodgson]

Hi
I've seen threads about making a field mandatory so the workbook can't be closed unless it's filled in, but I have a variation on this theme.
It's an expenses claim form, where if a value other than 0 is entered in a particular column (R), any row, being client entertaining expenses, then 2 other fields on the same row as the entered value (S & T) become mandatory, the name of the client, and the names of people being entertained (a text field with names seperated by commas, for instance).
Could anyone reply with a piece of vb and the details of where to put this code ?
thanks in advance
Peter
Ps. I've attached the draft claim sheet. It would also be nice if columns s &t were hidden unless an amount was entered in column r.

[Dennis7849]

See attached modified expense template.