OK, i'll have a look into those function. Though i've never used VB in Excel before. I was kind of hoping i wouldnt need to get involved with VB, but if its the only way to make Excel have negative times i'll have to. Thanks, i'll let you know how i get on.
You don't need to use VBA. Excel displays "######" when a cell contains a numeric value with more digits than can be fitted into the current width. All you need to do is resize the column to see the actual answer. (My mum used to impress her boss with this all the time!)
With regard to the answer that you need, try replacing
A positive answer will mean that the time spent was that much less than five; a negative answer shows how much more than five.