Hello

I am trying to make a field that i have created in sale.order mandatory for only newly created quotations upon custom module installation, and not to any past quotations(already existing before custom module installation) which might be opened to be edited.

This is my xml code:

This line of code makes this field mandatory for all quotations, both new and old. However, i want the field to be mandatory in only quotations that would be created after my custom module has been installed. 

Can someone please suggest something?

Thank you!