Jeff,
The trim for doors and windows in the 8.1 library is handled
by a macro that is called by most door and window scripts.
The sill and stool are not part of the trim macro and is handled
by another macro.
Altering the trim macro's code would be difficult and would probably
result in many unintended and hard to detect consequences.
This is probably one reason you have not received any (so far)
return posts concerning your request.
There is a way to accomplish what you want without changing
the trim macro and involves adding four parameters
to the parameter lists of the door and window objects
and adding a block of code in the 3D scripts.
I would be pleased to send you the code and explain how to use it.
If you are interested please e-mail me privately.
Peter Devlin