Sum Fields Based on Dropdown Selection

Question

I have (1) dropdown field named (CAT) that contains (7) items and repeats in (31) rows.  I also have (3) different decimal fields (REG, TIMEHALF, and DBL) which may or may not contain data, that also repeat in the same (31) rows.  Lastly, I have a separate field (BASEBLDGTL) that is not connected to the table, which I want to use to calculate the (3) different decimal fields base on the selection of the dropdown field.  So basically, I'm looking for the BASEBLDGTL field to add all of the REG, TIMEHALF, and DBL fields together for each row if the first item in the dropdown field is selected.  I also want the BASEBLDGTL field to be able to pickup on possible changes to the selection of the CAT dropdown field.  Any help would be gracefully appreciated as I'm a complete idiot in Java and FormCalc.

Answer 1

I'll give this a shot, but I'm not entirely sure what you're asking.
var amounts = xfa.resolveNodes("tblParts.Row1[*]");
var total = 0;
for (var i=0; i<amounts.length; i++) if (amounts.item(i).ddSomething == "abc") total += amounts.item(i).ExpenseAmount;
//go through the table, if the drop down matches what you're looking for, add that amount to the total
nfExpenseABCTotal.rawValue = total;