You might try using a combination of User Filters and Sheet Selectors. It will probably be a bit tricky and also somewhat difficult to maintian, but it should be doable. Here are some links:
Although ideally, you probably do want to have separate workbooks that are for different users. It can get challenging to manage multiple workbooks, but ultimately this will greatly simplify the maintenance of security.
Thanks Joshua. I'll read through those and test it out but it sounds as though we are actually doing it the recommended way. Thanks for the confirmation.
Good to hear! Glad to help!