1) Copy the below (it should all be on one line.

javascript:w=window.open(null,document.body.uniqueID);w.document.write('<title>JS Debugger</title><textarea style="width:100%;height:48%;" onblur="try{jsoutput.value=opener.eval(this.value);jsoutput.focus()} catch(err){jsoutput.value=\'(compile error)\\n\'+err.description}" wrap=off></textarea><br><textarea id=jsoutput style="font-family:monospace;font-size:smaller;width:100%;height=48%" wrap=off></textarea>');undefined

2) Make a new bookmark in IEWindows
3) Edit the bookmark's properties.
4) Paste the above into the properties. Click OK and 'yes' to the message about going ahead.

5) Go to your favorite website.
6) Press the bookmark on your button bar for the above.
...a new window with two panes should open
7) Type JS code in the top pane. Tab out or otherwise blur the field.
...the bottom pane will evaluate your code against the main window of your favorite website and put a result in the bottom pane.

You can use this to inspect the page (e.g. just type "document.body.outerHTML" in the top pane) or to manipulate it (change colors, styles, etc.)