[SOLVED] Can anyone help?

I was wondering if there is any kind of formula that will allow me to do this:

I have about 20 numbers. I want a combination of some of the numbers to add up to be (let's say) $25,768.45. I don't have to use all the numbers to make them add up to that number. I can use 2 or I can use all 20. Is there any kind of formula I can use to help me do this? The numbers are all big and the final number I need them to add up to is big too so I've just been plugging in numbers and guessing but it is taking forever AND I cannot make it work. I realize it may not work, but I thought maybe there is a trick or a shortcut to this. Thanks. Sorry if this makes no sense!