Comparing worksheets and carrying discrepancies over to another worksheet

Hello all,
I am trying to simplify my job by having excel do some of my work for me. I am trying to get excel to compare the quantaties of an inventory sheet to another worksheet's inventory and then have it carry over any negetive items into a sales order (in another worksheet). Before I start the project, I would like to know if this task can even be done in excel. It would help me out a lot if it can be done. I have tried to write macros in excel to complete this but that attempt failed. Any suggestions? All help will be useful.