Validation Script On Calculated Field

I have a field that totals a series of fields.  If the total plus another value of another field exceeds value of a third field than an alert message should be generated and the value be returned to 0.  The filed returns a false value whether the validation criteria is met or not.  Any assistance would be greatly appreciated!!!

var IDC0=Number(this.getField("IDC0").value);

var TA=Number(this.getField("TotalAward").value);

if(((Number(event.value)+IDC0.valueAsString)>TA.valueAsString));{

 
app.alert("Total of Direct and Indirect Costs Cannot Exceed the
Total Award");

   event.rc=false;

}