So, what's the bcm, or BAC, string that i need to crete/edit to add suck a thing?

For example, if i want to create a condition that autamatically untrasforms me, when my Stamina is less than 50, what and where i should check?

I tryed to check into the already existing ones, but got poor resoults.

Thx in advace, to whoever is answers.