Gilad, sorry for my ignorance but what does 'Code as string' mean?
Im trying to apply what you gave me and coming up short. Maybe the morning coffee hasn't kicked it..
this.getField("SUB-01").setAction("Calculate", event.value = (this.getField("PRICE-01").value * this.getField("QTY-01").value); if (+event.value === 0) event.value = "";);