Code field that copies to clipboard when user clicks on the field

I'm wondering how to do this:

I want to show a code field where the users can copy the code to their own site. Photobucket has a very nice way to do this (example)
When you click on one field, it puts the code in the clipboard.
I tried looking at their source, but this didn't work:

<input name="txtThumbURLTag2" id="txtThumbURLTag2" class="textBox" type="text" value="VALUE" readonly="readonly" onclick="trackCodeClick(event); copyToClipboard(this);">

Code (markup):

Anybody have a clue? I searched around a bit, but all the codes didnt seem to work in Firefox AND Internet Explorer.

 

use window.clipboardData.setData("Text", "mytext")
replace mytext with your text