Recognizing when text has been selected in textarea and what has been selected

[glz]

Hi I'd like to know if its possible to do this, and also if I could see a short example of doing such:
1. I want to recognize and act on (event handler) when text is selected, what I mean by this is that the mouse is held down and while its held down text is highlighted and then the mouse is released and the text highlighted
2. I also want to identify WHAT text has been selected everytime it is selected

I'd like to do this either in a textarea, or not in a textarea..

Thanks for looking.