I used this:
CAF.model('#{caf:cid("htmlGraphicImage1")}').element.width = 400;
This was based on some of the other messages on this forum. And it WORKS! 
I also had to add a “Mouse Out” event which restores the width back to 100. Again same code, just replace 400 by 100.
BTW if these is another way (referring to the control itself), I’d still like to know. What I mean is instead of using “caf:cid(…)” if there is a way to refer to the control itself…
#MWS-CAF-Task-Engine#webMethods#webMethods-BPMS