Custom Calculation Script Help - If/Then Statements

You can try this as custom calculation script:

var miles = Number(this.getField("Miles1").valueAsString);
var hours = Number(this.getField("Hours1").valueAsString);
var misc = Number(this.getField("Misc1").valueAsString);

var mileRate = (miles > 0 && miles < 100) ? 0.70 : (miles >= 100 ? 0.44 : 0);

event.value = (miles * mileRate) + (hours * 17) + misc;

If those are all calculations you are using for subtotal, you may consider using a loop to calculate all rows with one script and grand total instead of using a script in each row.

EDIT:

Script for loop, use it in "GRAND TOTAL" field as custom calculation script:

var grandTotal = 0;

for(var i=1; i<=10; i++) {
 var miles = +this.getField("Miles"+i).valueAsString;
 var hours = +this.getField("Hours"+i).valueAsString;
 var misc = +this.getField("Misc"+i).valueAsString;
 var sub = this.getField("Subtotal"+i);

 var mileRate = (miles > 0 && miles < 100) ? 0.70 : (miles >= 100 ? 0.44 : 0);
 var total = (miles * mileRate) + (hours * 17) + misc;
  sub.value = total;
  grandTotal += total;}


event.value = grandTotal;