Adjust AA% of hop in recipe, but maintain IBUs

I thought there was a tool or function for this in BS, but it appears I might be mistaken...

Is there a way to change the AA% of a particular hop in a recipe, and then have the quantity automatically update so that you maintain the IBU contribution of that hop? I can do this long hand I suppose, but we have a lot of recipes that I want to update using the AA% of our current hop inventory and was hoping for a slightly less manual method. Right now, I just use the "formula" of Amt of Hop X AA% of Hop in Recipe / AA% of Hop in Inventory. Not difficult math, but was hoping for a semi-automagic way to do this.

A hop substitution tool isn't part of BeerSmith. Though, I seem to recall it being on Brad's wishlist.

This may not be what you're doing but, I've noticed some brewers using IBU as a method to gauge hop flavor and aroma. They are not the same thing since the ratio of hop aromatic oils to bittering acids varies widely from hop to hop and crop to crop.

If the alpha acid content of your hop choices varies by more than 10%, you're introducing a flavor change (more than just the varietal change, alone), as well. Which is something you might not always want.

I think a substitution too would be useful, but there are some things the brewer needs to take control over. It's important that the brewer tell the computer what you want, not vice-versa.

Thanks. That's a good consideration. For the most part, the hops we have on-hand are within 10-15% AA one way or the other of whatever the "stock" value in BS is. Further to that point, most of these recipes have been vetted using the hops we have on-hand through multiple re-brews, so we know they work. In other words, we know that the bittering balance and the hop aroma/flavor profile is right--we just have to do the math every time since the recipes were designed around one hop statistic but implemented around another. When we move from the 1BBL system to the 15BBL system, we'll certainly be reformulating at that time, but this is mainly to simplify matters on the smaller system.