On Update Page, using OnLoad Body on a Template

Hi - I understand how to apply the list and select to the onLoad event of my BODY tag.

However my body tag is locked because of the template.

I've read this thread where Ray explains you can put the script in another place, without attaching it to an event and it will load on page load:

showthread.php?t=1844&highlight=body+onload

I'm having trouble understanding this though. Here is my JS that I took from the onLoad event I created on the body tag after I detached it from the template. It worked great - now I want to figure out where I can put it so I can put my template back:

WA_FilterAndPopulateSubList(groups_WAJA,MM_findObj('UserCompany'),MM_findObj('GROUP_ID'),0,0,false,': ');WA_setSelectionsInChildList(MM_findObj('GROUP_ID'),<?php echo $row_WADAusers['GROUP_ID']; ?>)

Any help would be greatly appreciated.

P.S. - love this Dynamic Dropdown tool. Kudos to you guys.