i did something kinda like that with some simple javascript:
function keepChecked(checkbox_this)
{ checkbox_this.checked = true; }
i use it with onClick for things i want to keep mandatory
onClick="keepChecked(this);"
so if you want it checked or not on page load, you'll have to access it. i would guess at document.formname.checkboxname = true/false.
keepChecked(formname,checkboxname)
{ obj = eval the statement "document." + formname + "." + checkboxname
obj = true/false }
something along those lines, can't remember the syntax right now.
oh yeah, and just call it with a php statement
IF (blah)
{ echo '<script type="text/javascript">keepChecked('.$formname.','.$checkboxname.');</script>'; }