[AccessD] Shell: preventing multiple instances of the app

...I'm opening a 3rd party app, non Office, using Shell ...I want to check 
first that an instance of the app is not already open and use that if it is 
...I have a module that I use the API from to do this with Access and other 
Office apps but I can't figure out how to do it from Shell.

...any help appreciated :)

William Hindman