@chadstenAug 26.2010 — #Try setting the value of the textfield to a javascript variable, and then changing it in your logic code. I guess I assumed you meant the textfield was client side.
Check out jQuery and see if it has anything you might need. Prototype is another great js library.
@FangAug 26.2010 — #If you want to paste from the clipboard then Flash is possibly the only option that works x-browser. This security loophole (using Flash) may have been closed by now.