Field Not Calculation Correctly
I am using the scripture below to add 4 fields and to be blank if the value is zero
var b=this.getField("BonusPY");
var c=this.getField("InterestPY");
var d=this.getField("OtherIncPY");
var e=this.getField("SalaryPY");
event.value=(b.value+c.value+d.value+e.value);
if(event.value == 0) event.value = "";
But everytime I test it adds incorrect at first and then correct when I enter the last number. For instance, if I input 1, 1, 1, and 1 it will calculate 1 + 1 = 11 then +1 = 21 then + 1 = 4.
What am I doing wrong? Please help.