For the booking system I am doing I have set up a workbook containing a booking form worksheet. In this I have a cell for the booking number to go in. I want this number to automatically change every time a new booking form is opened for data entry. A formula was suggested by a friend =SUM(previous number +1) But this wouldn't work - any ideas at all?!?!?!?! cos i'm stuck!! Thanks so much, Bex :D:D