JQuery :: Event With Named Function But Nothing Happens

I've been using jQuery for some time now but this is the first time I've run into something odd. Currently I'm developing a Theme for Concrete5.4.0.5, which automatically includes jQuery 1.4.2 - meaning, I can't use any other version of jQuery, that said: here is my problem.

I've got the following HTML (heavily simplified):
<nav id="mainNav">
<ul>
<li>Home</li>
<li>Text
<ul>
<li>Subnav</li>
</ul></li>
<li>Text
<ul><li>Subnav</li>
</ul></li>
</ul></nav>
<section id="contentWrapper">
...
</section>
And the following JS-jQuery Code (original, not simplified):
function hoehenAngleichen(){
if($('#mainNav').height() > $('#contentWrapper').height()){
$('#contentWrapper').height($('#mainNav').height());
}}
$(window).load(hoehenAngleichen);
/* works fine until here */
$('#mainNav li').bind('onmouseover onmouseout', hoehenAngleichen); //will not trigger

I want the "hoehenAngleichen" function to be triggered whenever someone is hovering or leaving a li-Element. But this code seems not to bind the events with the named function properly.