i have 3 text fields and need at least one of them to be completed in acrobat

var aF = ["ECONOMY TOTAL", "SP SVC"];

var sf = this.getField("EXPRESS TOTAL");

for (var i = 0; i < aF.length; i++) {

    var v = this.getField(aF).value;

    if (v !== "") {

        this.getField("last 4 digits").required

        break;

    }

}

I have 3 text boxes all numerical values only, EXPRESS TOTAL, ECONOMY TOTAL & SP SVC, I would like at least one of these text boxes to be completed with a value greater than 0. If one box has information then the other 2 textboxes are not required to be completed

I started with the above as a custom calculation script for each of the text boxes but am unsure if i am doing this correctly

Also should the form when opened have these text boxes as required ticked at source and only when one of these 3 text boxes is completed with a value greater than 0  the required state for the other 2 textboxes will be removed