Storing multiple solutions in a list

Hi

I am new to prolog. I have the following question

Assume I have a predicate defined f(X,Y) taking two parameters.

If X is a variable, or a partially instantiated variable (i.e. it is a 
structure), then assume X can have multiple solutions depending on the 
value of Y.

How do I store the multiple solutions of X in a list. The problem I am 
having is that once X is bound to a value, I am
unable to unbind it , to find the next solution to store in the list.

Maybe there is a differrent way of doing it, but I am stuck at the moment.


Thank you
Kandan