HELP!!

I need to know the formula (if there is one) for Excel to figure all the possible combinations of a given set of numbers that will add up to a specified sum.

In other words, if I give the following numbers 1, 2, 2, 3, 3, 4, 5, 5, 6, 7, 7 - I want Excel to figure all the possible combinations that will add up to 23, and also SHOW ME those combinations, and not just HOW MANY combinations there are.

i.e. one possible combination is 2, 2, 3, 4, 5, 7

Can this be done? What is the formula? I'm having a hard time figuring it out!!

Desperately,
Jenny