How to default warehouse on Pricing/Availability form

 Hope you can help sort this out:

Two orgs, each with its own product line, each with a single warehouse.  They do not cross at this time.

When our Order Entry people check pricing/availability they must manually input the Warehouse to get the information.

We have NOT populated the sourcing warehouse at the item level.

However, one Org's items ALL begin with "A/"  to tell them apart from the other Org.

So, theoretically if item X begins with A/ then CMO else LMO. 

Not sure where and how to set that up.

Thanks!

Cas'