Once the Search code is entered, you could set up UI rules with Error messages to prevent people from changing the value to something other than what you want. You could include the category in the rule's criteria, and have different rules for different categories.
We do this for certain categories that must have a certain suffix or prefix.
Warning. If you want to do sophisticated algorithms for checking the contents of the search code, you will have to do this using the Web API and programming the validation algorithm outside of OVSD.