Finding addends of an aggregate in a given set of values
 

Hello,
I wonder if anyone solved a problem similar to this:

assume an aggregate X and a set of values a, b, c, ..., zz; I want an
algorithm to tell me:

To obtain the aggregate X, you can sum the available values like:
a + c + e + ... + x, or
a + e + g + ... + x, or
c + e + k + ... y,
..
..
..

I know there is an Excel template with VBA routines by Tsushar, but these
become inefficient when the number of values increases to a couple hundred.
Deos anyone know of a feasible solution for, like - 800 values in a set?