MRP program - make MPF mandatory filter

Hi Community

Seek your advice/inputs on the challenge we encounter here.

Due to procurement department has assigned specific buyer to handle a particular group of item numbers in purchase orders, this is now causing some confusion in the MRP screen.

In MRP Detail screen, we were trying to filter out the list of messages, so that buyer A will only see his own assigned list of items. Currently this is grouped using the Master Planning Family PRP4 whereby each buyer handles a specific MPF code for a list of item numbers. We are trying to ensure that buyer A would only process his own assigned item numbers, but when he enters MRP screen, the form filter of MPF is "not" mandatory so he ends up seeing everyone else's item numbers, and sometimes may even other MPF items in error.