Cross-reference between plans

Summary:

We have a plan A with 2 types of populations. For one column we would like to have some people get their bonus from plan B (cross-reference) and have those values as read-only. For the others we would like that this information be editable on the plan A.

Content (required):

Hello experts,

We are facing issues trying to realise what we want on one plan of our plans,

We would like one column to be both a result of a cross-reference from another plan as well as editable on the plan.

The issue is that we would like for the inputs that are cross referenced to be in read-only while the other lines are in editable.