Out of the box, Captivate has only one 'hover' event which could trigger an action. That is for the Rollover Slidelet. It is possible to create events with either the HTML widget by InfoSemantics or with JS.
However, hope you are aware of the fact the Rollovers will NOT work on any mobile device, only when a mouse is used which means a laptop or a desktop? Is it a good idea to use that event?