Sorry guys... didn't mean to cause "handbags at dawn"
Thanks Todd...
You smarties are right, I'm crap at both IT and maths (including basic stuff I'm sad to admit) and although I could go back to school, I seem to get on OK by employing people who are good at boring stuff.
In this instance, both my technical engineers were out on site and I'm not going to ask my book-keeper or accountant such a stupidly simple question.
Anyway, job done now, and I did find an even more simple explination of what I wanted to do..
In an empty cell put 1.5 or 150%, copy it (Control C), then, select the range of numbers you want to increase, go to Edit, Paste Special, Values (or formulas, up to you), and also choose Multiply. Click [OK] and DONE !
Thanks all....
G