I assume that your tables are somehow linked to each other, e.g. by a common field ProductID (anyway, it would be helpful if you could describe your data model a little closer, to avoid our wild guessing).
There are lots of different solutions to your problem, like
a) JOIN the tables by common field
b) use a MAPPING LOAD and APPLYMAP() function
c) use LOOKUP() function in your load to lookup values from a different table
d) just do nothing (besides having the tables linked by ProductID) and do the calculation in the frontend
To select the right solution will depend on what you exactely want to do, so some small sample app attached to this thread or some sample lines of input data togehter what you expect as outcome would help us to help your.