Action: Onreturn on textfield

I've got a textfield, but i lik if i press the return button that he sould execute some code.
He should run the same code as the textbutton after it.
But how can id do that, there is no onkeypressed action on the textfield?

I found some javascritps on the net but mosly for onsubmit from a form, but its only a search textfield...
...