Making two dependent list box value 100%

Hi,

I have two list box elements. The values of each list box are:

0, 25. 50, 75, 100

GOAL: The value together should always be 100.

1) If I choose 25 on LIST BOX A then LIST BOX B automatically should be 75.

2) If I change the value of LIST BOX B to 50 then LIST BOX A should have 50 (GOAL)

For 1) I found this solution which I put as custom script within the list box setting calculation tab.

This works.

But If I  change LIST BOX B (2) there is no change of the value in LIST BOX A.

CODE for LIST BOX A

var newIndex2 = 0;
var field1 = this.getField("Dropdown1");
var field2 = this.getField("Dropdown2");
var selectedIndex2 = field1.currentValueIndices;
var newIndex2 = (4-selectedIndex2);
field2.currentValueIndices = newIndex2;

CODE for LIST BOX B

var newIndex1 = 0;
var fieldA = this.getField("Dropdown1");
var fieldB = this.getField("Dropdown2");
var selectedIndex1 = fieldB.currentValueIndices;
var newIndex1 = (4-selectedIndex1);
fieldA.currentValueIndices = newIndex1;

Any help? See attached file