Locating a user

I am using a program to remotely manage computers and support users while they are logged on. Our using move around a lot and are not always signed on to the same computers and a lot of the users are not computer literate. I have no way of located what computer a user is signed onto through this software that we are using. therefore we have to talk the user through determining their computername or IP address. Does anyone know of a program that will locate what computer a user is signed onto ifyou only know the username and do not know computername or ip address?