Excel 2003 moving data from a calculation to another cell

I have a workbook that contains order sheetsfor each month and an inventory worksheet. Each time an order is placed, I want the number from the “quantity” field to be susubtracted from its corresponding entry on the inventory sheet. I’ve used the vlookup function successfully in the price column to pull prices down from the inventory but is it possible to have a formula in one cell and have it place the results in another? It seems fine pulling data from other cells into the active one but doesn’t seem to go the other way. Help!