Call Events From A Single Function?

I´m trying to call both events "onMouseOver" and "onMouseOut" from a single function, but I just can´t seem to make it work.

Here´s an example:

JavaScript -

Code:
// Funcao teste
function teste()
{
onLoad = onMouseOut.images[0].src='../img/teste_menu.jpg'
onLoad = onMouseOver.images[0].src='../img/teste_menu_on.jpg'
}
HTML -


Code:
<a href=# onclick="sigem(&#3911;');" javascript:teste();><imgsrc="../img/teste_menu.jpg" width="100" height="20"></a>";