Restricting access to fields on position based on whether it's occupied

Hi everyone,

I tried doing a search but couldn't find anything relevant.

In EC, Position Management, I'm looking to see if there is a way to write a rule so that when a position is occupied, users with edit access (excl Super Admins) cannot edit certain fields like Job Code but if the position is empty, they can.

I'm unsure how to go about such a rule and don't have a partner so wondering if anyone has any ideas?

Thanks

Mala