Adjustment Calculation

Hello,

I have 3 fields that I am trying to get to do calculations between.

First field is called AP (for adjusted percentage) and settins is set to number with decimal point at 2 and vaule is set to 0. (this is for manually entering in a discount percentage ie .10)

Second field is called B (for sales price) that is also manually entered. Settings for this field are set to number.

Third field is called ASP1 (for adjusted sales price) Settings for this field are set to number and custom calculation script is:

// total purchase
var a = this.getField("B").value;
// discount rate of total purchase
var b = this.getField("AP").value;
// compute discount amount
var fDiscount = a * b;
// compute total puchase less discount, net purchase price
event.value = a - fDiscount;

When the data is entered it gives me a answer for the subtracted adjusted price.

Is there a formula that would give me the subtracted OR added adjusted price by some way of entering maybe the + sign or the - sign first and then gining me the adjustment price. ie +.10 OR -.10

Thanks