<img src="http://javascript.ru/forum/images/smilies/smile.gif" id="first" onmousedown="blabla();" />
<br /><br /><br />
<img src="http://javascript.ru/forum/images/smilies/unsure.gif" id="second" onmousedown="alert('Down');" />
<script>
function blabla() {
document.getElementById('second').onmousedown();
}
</script>