Make TW detect iframe src change

[Mat]

As some of you know, I set up a template on TiddlySpot so that Steve Schneiders TW students can easily get online TWs to work with. I'm happy to understand it is very much appreciated. I personally also use a similar template for my many experiments and creations. 

Now this template is based around an iframe showing a cut out segment of the original TiddlySpot setup page.

This looks good to begin with but as you'll note if you follow the instructions in the template, there is a confusing moment when the new tiddlyspot is created showing the confirmation page which doesn't fit the cut out anymore. It would be much better if the iframe could hide after the new tiddlyspot is created

According to this (and maybe even better, this) finding it should be possible using some kind of onload attribute in the <iframe> tag. (Both the original tiddlyspot page and the confirmation page are on the same domain.)

Just maybe something like this is already done with plugin libraries in TW? Anyway, I am hoping this can be used so that TW can "detect" this src change so that e.g some revealwidget could hide the iframe.

...but... could someone please help out with this? I have no skills in js. You'd be doing me and Steves students a service.

<:-)