Hi Alex,
Unfortunately the onMouseOver action has been removed from Xara animation options but still has an onclick action. The help file still says differently.
Attached is a xar animation that can create what you're after. It's just a quick and ugly example.
After having Xara create the swf I run it through Google Swiffy to create an html5 page which you should be able to place in an iframe in Wordpress. You won't be able to alter it via html or css though.
You can view the swiffy output HERE
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