change key figure to run snp heuristics????

Dear SAP,

now snp heuristic take in account current stock on hand when running. but i want to another key figure to replace key stock on hand to run snp heuristic.

For example:

Location K110 has demand 1500 and current stock on hand is 500, Key figure 'Ton kho ke hoach' is 700 so when running snp heuristic the system the number of receipt is: 1500 - 500.

But we want the system takes akey figure in account 'Ton kho ke hoach' it means that the number of receipt is: 1500 - 700

is it OK? if it's OK please show me how to do this.

thanks so much.