Since only IE seems to support the resize event on elements, you'll likely need to take a similar polling approach as I did with the window and text size. I checked in Firefox and the resize event never triggered on the element in question even though the width and height of the element did change in my test (was polling to see any difference).

So maybe what you could do is keep listening to timerpoke.wb and test for any changes. One thing you need to be cautious about is the impact on performance. If you are checking for any changes against a lot of elements on every timerpoke.wb then that could make things a little sluggish (or maybe it has not impact) so performance testing is very important.