Calculated field but if over an amount equals zero

I am trying to make a form that uses an input field (Estimated Sales Price of Current Residence) to calculate the Guaranteed Homesale Program value, which is Estimated sales price of current residence x  .15. But if the Estimated sales price of Current Residence is more than $750,000, then I want Guaranteed Homesale Program field to equal 0. I tried the following but an getting errors.

var n = this.getField("Estimated Sales Price of Current Residence").value;

if (n < 750000) {event.value = ("Estimated Sales Price of Current Residence * .15");}

else if (n > 750000) {event.value = "0";}