Records Read Only in Open UI

Dear Experts

We have a requirement to make Child records read only based a Parent Field Value. We are trying to figure out a way to do it at the UI layer (not using any BC user Properties or any Business Layer logic). Can we achieve  this in Open UI? We have not been able to figure out a way to do this without accessing DOM elements in a PR/PM file. However, this is not recommended. Can some one suggest an approach to implement the same?

Thanks in advance.