onchange or change help

onchange or change help

I have a test script on this webpage http://mlbshopgear.com/test/test.html it has an autosum of 3 boxes.
what i am trying to do is use the result of the autosum to directly multiply it in price. I've tried changing the codes to 
 $("#idPluginVersion").text($.Calculation.version);
 // run the calculation function now
 $("input[id=gawat]").bind("onchange",recalc);
 recalc();



and of course, in the reclac function of where the input woul be coming. Obviously i've changed the input box of sum to be readonly so that it would not be manipulated by the user. could anyone help me do this? i've already
search this 24 hrs and i couldn't find the answer. please help me.

anyway i've find this script in here:
http://www.pengoworks.com/workshop/jquery/calculation/calculation.plugin.htm

hope that helps and i hope that i've clearly stated the problem thanks