Random values for filters

I'm trying to write a script that will generate random values for the filter parameters everytime it is called. I'm new to java script and I'm just trying to get started with the examples from the scripts folder. Does anyone know how to fix this script to get random values for the Mosaic filters?
Thanks in advance.

// Copyright 2002-2007. Adobe Systems, Incorporated. All rights reserved.
// This script demonstrates how you can use the action manager
// to execute the Mosaic Tiles filter.

// enable double clicking from the Macintosh Finder or the Windows Explorer
#target photoshop

// in case we double clicked the file
app.bringToFront();

// debug level: 0-2 (0:disable, 1:break on error, 2:break at beginning)
// $.level = 0;
// debugger; // launch debugger on next line

if (!app.documents.length > 0) { // open sample file if no document is opened.
var strtRulerUnits = app.preferences.rulerUnits;
app.preferences.rulerUnits = Units.PIXELS;
var docRef = app.documents.add(320, 240, 72, null, NewDocumentMode.RGB, DocumentFill.WHITE);
app.preferences.rulerUnits = strtRulerUnits;
}

mosaicTiles( 12, 3, (15*Math.random()) );

function mosaicTiles( inTileSize, inWidth, inLighten )
{
// Get ID's for the related keys
var keyTileSizeID = charIDToTypeID( "TlSz" );
var keyGroutWidthID = charIDToTypeID( "GrtW" );
var keyLightenGroutID = charIDToTypeID( "LghG" );
var eventMosaizID = charIDToTypeID( "MscT" );

var filterDescriptor = new ActionDescriptor();
filterDescriptor.putInteger( keyTileSizeID, inTileSize );
filterDescriptor.putInteger( keyGroutWidthID, inWidth );
filterDescriptor.putInteger( keyLightenGroutID, inLighten );

executeAction( eventMosaizID, filterDescriptor );
}