New to VB programming, but not PHP. Simple plugin question

[kvnband]

OK - I am new to the world of programming products and plugins for VB, but not to PHP development in general. For my first project, I have created 5 custom profile fields in the admincp. We have a large, established user-base, and I need to make sure that these 5 fields are filled out, for tax purposes (We are a non-profit org).

So, how do I proceed? I basically just need to know how I check the logged-in user's custom profile fields at the start of each page load. I assume writing a small plugin is the way forward here, but aside from that, I'm completely clueless.

Any help?

Thanks!