Multiple Checkboxes

I have a spreadsheet that I record payments from customers on daily. There is a club that the customers can join. If the customer is a member of the club, I want to be able to check a checkbox on that row, and have the amount including the discount automatically sent to another cell.
so
cust no | custname | club memb | Check Amt | Amount less discount

The club memb column will have a checkbox, and if the box is checked, I want the check amount minus the discound automatically displayed in the last column.

I can get it to work if I code all the checkboxes individually, but I would have to code all 100 boxes... Any way to cut down on the code?

Any help is appreciated.

Wouldn't it be easier to use Validation? A simple "Yes" and blank option would make life easier in my opinion. It won't look as good but it would eliminate this hassle and possible future hassles.

Cheers!