Trade Management -- R12.2.X -- Locking rules - Options

Hi Trade Management Guru's

We are using R12.2.5 - Trade Management application.

Trying to leverage Locking rules to freeze few fields on Offer workbench and Claim Workbench --- As per document "Why are Locking Rules Not Working in Trade Management Claims Update UI? (Doc ID 2192965.1)"

R12.2.X -- the forms are upgraded to OA frame work -- traditional locking rules will not work on OA framework pages.

And Forms can be extendable "programatically"

I did not find relevant information on what needs to be done to extend forms programatically. Please share relevant information on how to extend forms programatically i.e primary purpose is locking few fields when the offer is active.