javascript in LiveCycle forms

I am no programmer, however I will be giving an introductory class on Adobe Pro 8. I am showing different examples on the different interfaces (both an Acroform and a LiveCycle form). On the Livecycle form I show an example using formcalc and the script editor, but I cannot for the life of me figure out the same calculation using JavaScript. Is it even possible to use javascript & Sum function in a liveCycle designer form? I have checked a couple of places and am getting opposing information.
 
I know in Acroforms you can do a custom calculation like this:
 
var f = this.getField("odomstart2");
var g = this.getField("odomend2");
event.value = g.value - f.value;
 
but that does not work in xml forms. Is something like that possible, or should I just give up?
 
Thanks a million,