How to add to a result

I have a table in my database that is a base table for my blind companys. Each company can share the same price table.

(This price table only hase 5 columns in it)
1. BlindSizeID(KEY)
2. Maxheight
3. Price
4. CompanyID (FK)
5. ProductID (This one might take a hike)

Anyway, i am connection these to a set of dropdowns that are on the UI.
For instance one Dropdown will be the width and one will be the Height and One will be the company (Blind Maker Of Choice (Thier options of company)).

Here is my question they all can sell the same product; however, their priceing is all eaither a little higher or a little lower than each other. Is it possiable (Without recreating the wheel) to add or subtract the result that is returned from the stored query?

Should i do this all in the database or just the application..??

Thank you!

Erik...