Having a running service open a window?

Question

Hi.  I have a program that has two functions; one is to be a service and do some work behind the scenes and the other is to provide system information for our helpdesk so when a user calls in, we can have them run the program and tell us what their PC name is, IP, etc etc.  Right now, to run as a service you do executable.exe /svc and to get the info, you just omit any switches.  I was thinking, the boxes all will have the executable running at all times as a service.  It'd be cool if there were a way to pass a command to the running service to open a dialog to show the information screen. 

I suppose it's frivolous, as it doesn't matter much to just open it a second time but I was just curious if that's possible.  I see services have the option to interact with desktop, sounds like what I'd want to do but I'm not sure how to programatically implement the "interrupt" to the service to let it know to fire off a thread to do the display work. 

How would you do that?  Thanks!