If statement in my Simplified field notation?

[Deborah26470382gwb2]

I finally got this to work and the result of this equation goes into a SubPayment field: 

WeeklySalary-EIPayment1*WeeklySalary1

However, when there is no amount in EIPayment1 I want the result to be zero in the SubPayment field.

Is there a way to do this? I am a brand spanking new user......

[Bernd Alheit]

If statement is there not possible.

[Deborah26470382gwb2]

how can I get the SubPayment field to show a zero or blank if there is no amount in the EIPayment1 field but do the cal I mentioned if there is

[Nesa Nurani]

Use this as custom calculation script of SubPayment field:

var ws = Number(this.getField("WeeklySalary").valueAsString);
var ws1 = Number(this.getField("WeeklySalary1").valueAsString);
var ep = Number(this.getField("EIPayment1").valueAsString);

if(ep == 0)
 event.value = 0;
else
 event.value = ws-ep*ws1;

[Deborah26470382gwb2]

Thank you so much!!!!!!!