Make cells read only after a while or by permission level

Question

I have a form that will be sent out to different people. I have different columns, ones for the yearly target and others for the quarterly results.

I want the users to be able to see the targets, but not be able to edit them after Q1. Is there a possibility to set it that you need a certain permission level to edit those columns. Another idea is to have a workflow that "locks" the columns after some time (we can use Nintex, but not SharePoint designer). Is it just an easier solution instead of them being a drop-down list to them being a column with fixed value?

I'd appreciate any help you can give me!

Answer 1

This is similar to this question that asked about column level security. Column level security doesn't exist in SharePoint. You could certainly use a custom forms via PowerApps to change how fields are presented based on conditions, though same as in the other answer, this isn't permissions, and diligent users could still find other ways to edit the data.

Of course, the standard PowerApps warning applies: it's a neat tool, but it can also be frustrating and buggy, so proceed with caution.