Help with List/menu

Thanks to everyone who help me last time. This one I tried but failed! I have
to javascript for the item

javascript:MM_showHideLayers('layer','','show')

but I cannot not get it to work in my list/menu

<select name="choice" size="1" onChange="jump(this.form)" >
<option value="">Product Selector</option>
<option value="javascript:MM_showHideLayers('profile','',' show')"
selected>item</option>
</select>

any help would be great thanks.