code runs on change to layout?

Here's a knotty problem. I have a project with three different sets of plans, one each for options A, B, and C. There's a field in model space that pulls the current option name from a drawing property. That field appears on all three plans. At present I can redefine that property to the option I'm working on, but I have to do it manually. My question is: can I tie a lisp function to a layout tab (or set something else) so that when I switch to a particular layout, the drawing property is given a particular value? For instance, if I switch to the layout for plan 100B, which is part of option B, the drawing property becomes "B" automatically. Thanks for any advice.

Over a hundred people took the time to read my post, so thank you. I didn't think there was a solution for this, so it's nice to have the experts agree with me.