Call Park Group - making it work

Hi - We set up a Call Park Group with seven phones in one department. Calls come in big bunches to this department at peak ordering times. The salesmen are checking stock and building orders, so they might be anywhere around the property. The receptionist wants to Park up to five calls at a time, then find the right salesman and let them know which line to pick up (from any phone). Since there are seven phones in the Group, she has seven spots where calls can be parked. There are also one or two other phone answerers who want to park a call. Here's the problem - They can't tell which extension is available to park the next call. They try to Park a call on an extension with a parked call already, and they get a busy tone. Is there anyway to "see" which lines are available to Park a call? Maybe if the receptionist had a Sidecar (VVX Expansion Module)?