Flash 2004 - ActionScript (ComboBox)

I have 2 combobox and I would like to add control for each of them
let say:
1st combobox (cmbP) - 1, 2, 3, 4, 5
2nd combobox (cmbC) - a, b, c, d,e

block value "4" and "5" in cmbP  if user choose "d" or "e" in cmbC
and else, user could choose 1 - 5 for vlaues from a - e

I have tried to use the following code, but when I choose "e", actually the value "4" and "5" still keep in the combobox without any error.

Anyone would help, Thanks

var cbP = new Object();
cbP.modelChanged = function(evt:Object) {
   switch (evt.eventName) {
      case 'removeItems' :
         trace("Removal");
         this.cmbP.dataProvider = evt.target;
   }
};
cmbP.addEventListener("modelChanged", cbP );
 
var cbC = new Object();
cbC.change = function (evt) {
  if (cmbC.selectedItem.label=="d" || cmbC.selectedItem.label=="e") {
     cmbP.removeItemAt(3);
     cmbP.removeItemAt(4);
  } else {
     if (cmbO.length <5){
        cmbP.addItemAt("4");
        cmbP.addItemAt("5");
      }
  }
}
cmbC.addEventListener("change", cbC);

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