Unfortunately, you cannot create the same constraint association on the data grid search filters.
Try leveraging the constrained by that you used in the web form and create your own search fields that will populate the data grid. You'll need to create an association that would be refresh when you submit a new search. Associate the entity that you are returning with an account object via reference set (if no other association is being used). Then update the association with the results of the search and set the Xpath of your data grid to I.E [Administration.AccountYourEntity = '[%CurrentObject%]']. This would allow you to display your targeted search results and validate/contrain your search filters as you see fit. OR Create a new Attribute that contains the valid combinations of the CategorySubCategory (assuming it's not a huge list) and add to the search/grid.