Modelling the register fields via callbacks

I need to model several registers in RAL.
For example, some bits are tied to zero (in a RW field).
Another example: a RW field keeps written value or not depending on other fields value.

What is the best method to do the modelling? Is it ok to use post_write cb to model the fields based on the constraints above?
There are reasons for post_predict(), but this is a field cb and i need to manipulate data between fields.
Thanks!