Anyone know why this doesn't work in IE5/5 but does in Netscape4+?

Code:
 <select size=1 name=month onchange=this.blur()>
The reason for attempting this is because users with a wheel mouse often select a date and then try to scroll down. Because their focus is still in the select box, the date changes. Often the user doesn't even notice this. So, I want the focus to be removed once the date has changed.

TIA, brian