Validate 2 fields

Question

I have two fields I need to have validated (equipment and serial numbers). Once those are filled out the user will use a dropdown(tonnage) to select a number that will return them a specified dollar amount (working fine). My issue is validating those two fileds and if they are not filled out the dropdown needs to be blank. I have the following code that I believe to be correct. I am calling this function in the validate section of the dropdown field and NOTHING is happening. I'm at my whits end  - any suggestions are helpful.
function getEquip() {
    var rowName = event.target.name;
    var rowNum = rowName.substr(rowName.length - 5, 5);
    if (this.getField("Equipment Description" + rowNum).value == " " && this.getField("Equipment Serial" + rowNum).value == " ") {
      this.getField("Unit Tonnage" + rowNum).value = " ";
    if (this.getField("Equipment Description" + rowNum).value == " ") {
        app.alert('Please enter an equipment description');
    if (this.getField("Equipment Serial" + rowNum).value == " ") {
        app.alert('Please enter an equipment serial number');
Image of PDF

Answer 1

I checked the box that commits the selection.
I'm not sure about accessing 'event.value' to check the value of the field. The dropdown operates on a different code (below) and that part is working perfectly. It's just the checking part that won't work.
function getIncentives() {
var rowName = event.target.name;
var rowNum = rowName.substr(rowName.length-5,5);
var tons = this.getField("Unit Tonnage" + rowNum).value;
if (tons == "4") {
  this.getField("Incentive" + rowNum).value = 250;
if (tons == "5") {
  this.getField("Incentive" + rowNum).value = 250;
if (tons == "6") {
  this.getField("Incentive" + rowNum).value = 265;
if (tons == "7.5") {
  this.getField("Incentive" + rowNum).value = 287;
if (tons == "8") {
  this.getField("Incentive" + rowNum).value = 295;
if (tons == "9") {
  this.getField("Incentive" + rowNum).value = 310;
if (tons == "10") {
  this.getField("Incentive" + rowNum).value = 325;
if (tons == "11") {
  this.getField("Incentive" + rowNum).value = 340;
if (tons == "12.5") {
  this.getField("Incentive" + rowNum).value = 362;
if (tons == "15") {
  this.getField("Incentive" + rowNum).value = 400;
if (tons == "17.5") {
  this.getField("Incentive" + rowNum).value = 437;
if (tons == "20") {
  this.getField("Incentive" + rowNum).value = 475;
if (tons == "25") {
  this.getField("Incentive" + rowNum).value = 550;
if (tons == "30") {
  this.getField("Incentive" + rowNum).value = 625;
if (tons == "35") {
  this.getField("Incentive" + rowNum).value = 700;
if (tons == "40") {
  this.getField("Incentive" + rowNum).value = 775;
if (tons == " ") {
  this.getField("Incentive" + rowNum).value = "";