Query/Script to add user to group based on field in sys_user table

Hello,

In our sys_user table, the department field changes frequently.

I'd like to have a user be added to a group if department = x, but also have a user be removed from a group if their department changes from x to something else (y).

I am fairly new to SN, and have experimented with a business rule on the sys_user table that interacts with the sys_user_grmember table.  This has had limited success with some buggy behavior.

I'd like to be able to run 1 clean script that updates all users based on their department being x or y, then have an active rule that looks for updates to the department field and associates or removes that group going forward.

Many thanks for any and all help,

--Robert