Reference Non db field???

[fuzzy1]

Before over thinking my question, I'll try and state it plainly first.
How do I reference a non db field (ie checkbox) which if empty (not checked) will satisfy the conditions of a function?

Below I have attempted to outline the basic archetecture.

// db table/field == contacts/flag

Module = Contacts
vardefs.php
Contacts.php
ListView.php
ListView.html
<input type="checkbox" size="1" id="clear_flags" name="clear_flags"{CLEAR_FLAGS}></td>

function and call
function clear_flags() {
if($empty($_REQUEST['clear_flags'])) {
$query =' update contacts set flag="off" 'or die('UNABLE TO CLEAR FLAGS');
}
}

clear_flags();

[zabmilenko]

Set the value in the checkbox field:

<input type="checkbox" name="key" value="checked">

Then if $_POST['key'] == checked, then they checked it. Otherwise it would be an empty field. You will then have to code your handler around that.