Sharing of licenses

We are a small office with 4 network licenses.  The licenses are share betweeen two locations.  There are times when we have to ask a user to return a license.  Currently the only method is to call the person.  This works fine now, but we are thinking of growing and controlling more licenses.  Does anyone know of an automatic method to notify and then return the license to the server?

Thanks

SolidworksAdministration