Prevent PortableApp from Launching additional instances?? Functional setting question

I have made a concerted effort to research this, and I am quite sure it can be done since i remember reading something about it a long time ago...

Basically i just need to know how i would restrict a 2nd or additional instance of the portableapp io developed to be run. I think i remember a setting somewhere... in the appinfo or launchsettings config files.... where if you set it.. it will prevent a 2nd instance of the app from running... that's what i need.

Any help appreciated.