who you can't log in as, but you can su over to them once you get on.

I am aware of how to make a no login user by using /NOSHELL in the spot for the shell in the passwd file, but my question is if I do that and then get on the box as a user who I can log in as and "su -" over to the nologin user when I hit his environment and it reads the variables to set it up will it see that and not let me log in as them or will it work out OK?

I realize if I "su" to them I just get theri permissions, but if I need to also use their environment (ie "su -") then what do I do?

Any help is appreciated, Thanks in advance,
New_Guru