I'm trying to write a formula for using a spreadsheet for my doules bets as it takes me 4 hours to do it by hand with pen and paper as i do a min of 4 daily doubles each saturday with 10 horses in each leg. It needs to update if there are any scratchings.

This is my attempt at the formula.

In cell a is the tab no. cell 2 is the odds.

B1 3.70 odds leg1
B2 4.20 odds leg2

tab no.
odds leg1
odds leg2
doubles price-1
amount to bet per combination

=b1*b2-1.

as you can see I get confused at this point. Can someone please help?