I have a workbook that has 10 different sheets with names ranging from
"Finance" to "Operations." What I would like to do is have the application
review the username upon opening and then run it against a list to first see
if that username is on the list. If it isn't, then nothing will open.
Secondly if it is on the list, I would like it to compare accesses to the
sheets, i.e.:

dsmith works in Operations
brogers works in Finance
mwilson works in both Operations and Finance

Dsmith should be able to view the "operations" sheet and nothing more, just
as brogers should view "finance" and nothing more. However, mwilson should
be able to view both the "operations" and "finance" sheets, but none of the
other 8 remaining sheets.

I am not sure where to even begin.