Serial Numbers

Hi,

The attached spreadsheet works out serial numbers for vouchers (they're not real serial numbers). So, for £20's, I type in the first serial number, it counts how many that person needs and shows the last serial number that person will have and then does the same again for the next person. The problem is, I can't just autofill this formula as for example if somebody is only having £5 they won't need a £20 and so I need to renter the formula manually on the next person who has a £20.

Can anybody think of a way that it can check whether they need for example a £20 and if not move on to the next one that does need one?

Sorry if I've not explained that well, thank you for looking.

This proposed solution employs formulas.
The 'Start' formulas are all similar to: =IF(B3=0,"",MAX(F$2:F2)+1)
The 'Start' formulas will need to be placed in the second row that has a value (the initial value would have to be manually input) so that you'll find the first formula for £5 in cell I6.
The 'Stop' formulas are all similar to: =IF(E2="","",E2+B2-1)
The 'Stop' formulas all begin in row 2 of their respective columns.
Let us know if you have any questions.