Note icons on the archives page

Tinderbox does this cool thing in outlines where the icon changes based on the age and size of each note. I'm working on mimicking that feature on the Archives page here. I'm a little lost when it comes to the new "functions" features in Tinderbox 9.1 so I fell back to adding some Action code as an Edict. Like this...

if ($TextLength>500) {
    	$NoteIcon="long.png";
}
if ($TextLength>50 & $TextLength<=500) {
    	$NoteIcon ="medium.png";
}
if ($TextLength<50) {
	$NoteIcon ="small.png";
}
if ($Image) {$NoteIcon = "cam.png"};