Unlock User Account

Anyone know of a command line tool in the res kit, or elsewhere off the top of their heads that, when run, will unlock a user account?
The situation is we are trying to create a Task Pad through mmc that will allow a group to Reset Passwords, and Unlock Locked accounts, ONLY. Problem is, that the options under menu commands includes only a few items, like Reset Password, but NOT Unlock Account. So if we create one that uses a command, rather than a menu item, I need a commandline tool that cando this… any ideas?