Stock Levels with "Packs" of Products

[drchad]

Hello there,

I'm hoping someone can help me with an inventory issue. 

My shop sells mostly paper products, sold in "packs".  So for example, we sell brochure titles in the following combinations: Pack of 25, Pack of 50 and Pack of 100.  These combinations are in a drop down menu associated with each brochure title.  For inventory, I want to only keep track of the base level "pack" - which would be 25 in this case (this is how we store them in our warehouse). If a customer orders a pack of 50, I want the inventory to deduct 2 packs of 25 instead of 1 pack of 50.  If a customer orders a pack of 100 I want the inventory to deduct 4 packs of 25 instead of 1 pack of 100.  

Does anyone know if such a modification or module exists to accomplish this? I know you can make product bundles but this doesn't solve my issue since I have multiple quantities of paper products within each product title.  

Thanks in advance for your help!

Chad