VPN

I am trying to set up a VPN for my employer but he also wants to be able to IM his employees. The reason for this is because a couple of people work from home and he wants to able to communicate with them at all times. My problem is that the IM no longer works with the VPN. I am new to this and would appreciate any help. I understand how the VPN works, is there any way to also have the IM work at the same time? Thanks for any help.