Join/Leave Groups

Hello,
I’ve got a question related to Joining and Leaving groups,

We’ve got a helpdesk, wich incoming calls are forwarded to, thou some the shifts for taking the phone changes daily, and the phone needs to stay on for internal calling,
So now my question, is it possible to setup so the ones who require to get incoming calls to join a group by pressing, for example “*21”

Thanks in advance

Anyone?