Manually adding username validation

Hi,

I have my own registration form (I load the form object via get_user_register_form()), but print out only $register_form->form_start/submit/end as a wrapper, and add the other fields manually). What I'm trying to do now is add the username originality check. I've tried wrapping the elements in the appropriate div's/CSS classes, but that didn't really work out for me. Here's how I did it:

<div id="username-check-wrapper">
     <input type="text" class="textfield_user" value="Korisničko ime" name="name"
     onblur="this.className='textfield_user'; if(this.value==''){this.value='Korisničko ime';}"
     onfocus="this.className='textfield_user_active'; if(this.value=='Korisničko ime'){this.value='';}"
     onmouseout="if(this.className!='textfield_user_active'){this.className='textfield_user';}"
     onmouseover="if(this.className!='textfield_user_active'){this.className='textfield_user_hover';}"
     title="Dozvoljeni karakteri: a-z, 0-9, _" />
</div>
<div id="username-check-message"></div>
<div id="username-check-informer" class="username-check-informer">&nbsp;</div>

Is that completely wrong? What am I missing? Thanks!