I try to make function for due payment. When I made copy file and then drag
down the formula and it's succed. But for the cell that I not fill yet has
due date also.
How to make that cell became 0 (zero) if not fill the cell yet.

example :

A1 A2
19/8/05 =A1+30
- 30/01/00
- 30/01/00

Thanks

Lando