Well, 2 ideas, actually, that might be worth trying.
First, have you tried STYLE: ? Most HTML entities provide for styles, maybe FORM does too...
Next, since you're already using the javascript submit(), why not go whole-hog? Make a function like
function mySubmit(theSubmitType)
if(theSubmitType==1) {username='phpguru; submit();}
and set
<A onclick='mySubmit(1)'>
etc.