copying text from my cocoa application to another

I have a cocoa a开发者_Go百科pplication, that on pressing a certain key gets selected text from the frontmost application and processes it. Now I'd like to replace the selection that it took with a processed text. How do I do it?

TIA

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Look into the services system...

http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/SysServices/Articles/using.html#//apple_ref/doc/uid/20000854-CEGDDHJJ