Do you get any errors popping up?
You also need to specify the target or object into which you want to place the result.
event.value = this.getField("AmountFinanced").value * Math.pow(1 + this.getFieldI"Rate').value, this.getField("NumberofPaymentsRow1").value) ;
Here's what I ended up using: event.value = this.getField("AmountFinanced").value * Math.pow(1 + this.getField("Rate").value, this.getField("NumberofPaymentsRow1").value/12) ;
The /12 made was to get the term in years rather than payment installment. Thanks again.