This article contains code to do want you want:
http://www.mvps.org/vbnet/code/subclass/registerhotkey.htm-Ed
>I am working on an application where I'd like to have Hot Keys CRLT+XX to perform different functions, my problem is I need the keys to function even if my app is minimized and another app has focus. Can this be done??
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>Any thought would be great.
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>Rich Imbruglio