You're right -- I meant HBUs. I'm thinking that it would be even better if I could actually record the recipe as calling for X HBUs of hops, rather than having it do the conversion as I'm creating the recipe.
My thinking is that depending when you add the hops, you may be more concerned with amount of alpha acid or the weight of the hops.
For hops that boil, say, 60 minutes, all you really look at is the HBUs, and you really don't care at all how many ounces. If you're dry hopping, the HBU's become similarly irrelevant.
Perhaps instead of a single "add hops" button in the recipe screen, there could be a one that says "add bittering hops" and one that says "add flavoring hops." Bittering hops would be saved as HBU's, flavoring hops as ounces. That or the add hops dialog box could allow you to specify whether you want the hops saved as ounces or HBUs.
When you're entering the info for the bittering hops, you could enter "X ounces at Y% AA" and have the HBU calculation done on the fly as you're describing.