Auto-fill a text field with a popup window when a radio button is selected.

I have a button labeled Military.  When a user clicks on that button, I have a window that pops up asking if they're Active Duty, National Guard, or Reservist.  I'm asking them to input a number representing one of the three choices and then another field auto-fills their choice when they click OK.  Otherwise the field is blank.  Here is what I have so far, but nothing is auto-filled into the other field:

var vMil = this.getField("13: Persona");
// Display Response Box
var vMilInfo = app.response("Input the number representing your military status.\n\n1) Active Duty\n2) National Guard\n3) Reservist"," [Box 9 - DESIGNATION OF PERSON]");
switch(vMilInfo){
 case "1":
  vMil.value = "A = Active Duty";
  vValidResponse = 1;
  break;
 case "2":
  vMil.value = "N = National Guard";
  vValidResponse = 1;  
  break;
 case "3":
  vMil.value = "V = Reservist";
  vValidResponse = 1;
  break;
  vMil.value = "";
   }

I'm doing this in Adobe Acrobat PDF form.