Perms through plugin php

Hello
Iam just curious to know if it is possible to give a custom usergroup perm to use a plugin by editing the php file of plugin ??.
I hope it is.

if you dunno then suggest me a good plugin which is publicly released ?? to give custom perms of using plugins for custom group :D just like that custom location in this forums.
:noh:

Thx.K.BYE.