Formula must produce two positive numbers otherwise an error message

Hi there,

I want to create a spreadsheet where:

1. Odds -- I enter two lots of 'odds' (can be any odds e.g. odds # 1 $1.50, odds # 2 $2.00)
2. I want the formula to work out how much money is required to back both odds (e.g. formula works out how much money I must back both odds to make a profit, i.e. 'total money won' minus 'total money down' and if both 'win amounts' are 'positive numbers' (not negative numbers) it means I make profit from backing both bets with the money down the formula has produced).

If there is a negative number in 1 or more 'win amounts' # 1 or win amount # 2 that means my bet fails and the formula displays 'Error - bet failed'. The formula must produce positive numbers for both bets for a successful bet. (i.e total winnings from both bets must be more than money down for bets # 1 and bets # 2.

Please see pic for clarification.

I hope it's not too confusing.

Thanks

Simon