RSSP mixed requisition lines

Summary:

When submitting a requisition we would like to check if all the lines are of the same type and block the users from submitting such requisition. We have provided training materials for users to avoid such situations. Nevertheless we have a large user population and some of them are using RSSP sporadically. As long as technically it still is possible to submit such requisitions (as it is a standard practice) users will continue to do it therefore not abiding to the company's internal regulation. Only catalog lines or only non-catalog type or only punchout types.

Is there a way to add a validation message to check this before submitting a requisition?