Is there a way to programmatically trigger the onmouseover event in plain JavaScript? or extract the method from the onmouseover event to call it directly?

eg

<div id=bottom-div onmouseover=myFunction('some param specific to bottom-div');>

    <div id=top-div onmouseover=????????></div>

</div>

top-div is above bottom-div, so the onmouseover won't get fired in bottom-div. i need a way of calling myFunction('some param specific to bottom-div'); from top-div