What Javascript event is triggered in moving shuttle items to the right?

Question

Application Express 3.2.1.00.10
I've tried onclick, onblur, onfocus, onchange, but none of them fires immediately after moving all shuttle values to the right using the >> (select all). My alert message is only displayed once the user selects all and clicks again on one of the shuttle boxes (left or right side). The user is suppose to be limited to selecting only 20 values. I would like an alert to be prompted before the page is submitted.
Page Item Name: P27_ALM
HTML Form Element Attributes: style=''width:200px;'' onchange=''limit_ALM();''
Javascript function included in the page attribute HTML Header section:
function limit_ALM(){
  var count = $v('P27_ALM').split(':'); 
  var maxCount = 20;
  var selObj = document.getElementById("P27_ALM_RIGHT");
  if(count.length > maxCount){
    //clear shuttle
    selObj.options.length = 0;
    //g_Shuttlep_v15.reset();
    alert("Only up to 20 Available Labor Markets (ALM) may be selected.");
    return(false);
   else {return(true);
}

Answer 1

camickr
Your example of creating multiple editors is not my preferred solution. However, I was able to use the idea to create a solution that does work.
My data structure being displayed by the table is composed of containers and elements. A container maps to a single row and an element is a cell in that row. Each element is able to determine its list of possible values. When the editor is being configured via the getTableCellEditorComponent() method the element is associated with the editor. The combobox would then set the elements possible values into its datamodel when PopupMenuListener.popupMenuWillBecomeVisible() is called.
What I ended up doing was loading the elements possible values first, then creating a new combobox with the possible values as a parameter to the constructor. All this was done in the getTableCellEditorComponent() method. This is a hack, but one I'm willing to live with.
Thanks for your time.
Zac