TileList Add/Remove function problems for a flex beginner

Question

I am starting up a new project for my university course which will allow users to drag and drop icons into their own area.
I wanted to use a TileList to provide the buttons for the users to select their area i.e. when a user clicks on a button in the TileList their area will be shown then they can drag items into it from another area that will always be shown (these items will later act as links to websites effectively making this application an interactive favourites menu but I'm nowhere near that point yet).
The thing is I also wanted the user's to have the ability to add a new user or remove a selected user by clicking buttons to either add a new user or click a button that will delete a selected user however after searching the internet for code and using it in my application it's a little but messed up.
The problem is I have created an array of 5 profiles (slots for each user) but I only want each slot to be added once whereas at the moment I can remove buttons easily using the remove item button when a user button is selected but if i add a few profiles then delete one and add another sometimes there will be 2 instances of the same button added. I only want ONE of each profile button from the array to be viewable in the application at any one time. It's hard for me to explain this so heres my full code for the applicattion. I'm sure it just needs slightly tweaking but if someone could edit it for me it would be greatly appreciated as I'm totally stuck:-
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" xmlns:components="components.*" backgroundGradientAlphas="[1.0, 1.0]" backgroundGradientColors="[#545351, #E3DFDF]">
   <mx:Script>
      <![CDATA[
         import mx.managers.*;
           private var _dragManager:DragManager;
           private var _historyManager:HistoryManager;
           private var _popupManager:PopUpManager;
           import flash.net.navigateToURL;
           import flash.net.URLRequest;
           import flash.net.URLVariables; 
           import mx.events.ListEvent; 
           import mx.controls.Button;
            import mx.collections.*;
            import mx.controls.Alert;
      ]]>
   </mx:Script>
    <mx:Script>
        <![CDATA[
            import mx.effects.easing.Elastic;
            import mx.collections.ArrayCollection;
            [Bindable]
            private var myDP:ArrayCollection = new ArrayCollection(
            private var dpArr:Array = [{label: "New Profile 1", data:1},{label: "New Profile 2", data:2}, {label: "New Profile 3", data:3},{label: "New Profile 4", data:4}, {label: "New Profile 5", data:5}];
            private function deleteItem():void {
                // Remove item from Array Collection
                if(myDP.length > 0){
                    var toRemove:Array = [];
                for (var i:int = 0; i < tlist0.selectedItems.length; i++)
                    toRemove.push(tlist0.selectedItems);
                for (i = 0; i < toRemove.length; i++)
                    myDP.removeItemAt(myDP.getItemIndex(toRemove));
            private var zcount:int = 0;
            private function addItem():void {
                // Add item from source Array to Array Collection
                if(myDP.length < dpArr.length){
                    myDP.addItemAt(dpArr[myDP.length],myDP.length);
             private function tileList_itemClick(event:ListEvent):void {
            private function showAlert(event:ListEvent):void{
              Alert.show("You clicked button #"+event.currentTarget.selectedItem.data);
        ]]>
    </mx:Script>
    <mx:Sequence id="itemsChangeEffect1">
        <mx:Blur blurYTo="12" blurXTo="12" duration="300" perElementOffset="150" filter="removeItem"/>
        <mx:Parallel>
            <mx:Move duration="750" easingFunction="{Elastic.easeOut}" perElementOffset="20"/>
            <mx:RemoveItemAction startDelay="400" filter="removeItem"/>
            <mx:AddItemAction startDelay="400" filter="addItem"/>
            <mx:Blur startDelay="410" blurXFrom="18" blurYFrom="18" blurXTo="0" blurYTo="0" duration="300" filter="addItem"/>
        </mx:Parallel>
    </mx:Sequence>
   <mx:Canvas width="1168" height="716" backgroundColor="#0219FB" horizontalCenter="0" verticalCenter="0" borderColor="#000000" borderStyle="solid" borderThickness="1" cornerRadius="20"  backgroundAlpha="0.8">
      <mx:Canvas id="UserArea" left="10" x="0" y="49" width="670" height="594" backgroundColor="#000000" cornerRadius="20" borderStyle="solid">
           <mx:TileList id="tlist0" itemClick="{showAlert(event)}" itemRenderer="mx.controls.Button" top="10" left="10" right="10"  color="#FFFFFF" height="50" width="100%" fontSize="12" fontStyle="bold" columnCount="5" rowCount="2" direction="horizontal" dataProvider="{myDP}" itemsChangeEffect="{itemsChangeEffect1}" backgroundColor="#000000" fontWeight="bold" borderStyle="none"/>
           <mx:Canvas x="63" y="129" width="200" height="200" fontSize="36" borderColor="#FFFFFF" id="Canvas1" visible="false">
              <mx:Label x="27" y="25" text="Profile 1"/>
           </mx:Canvas>
      </mx:Canvas>
      <mx:Button label="Remove item" click="deleteItem();" color="0x323232" x="96" y="10"/>
      <mx:Button label="Add item" click="addItem();" color="0x323232" x="10" y="10"/>
   </mx:Canvas>
</mx:Application>

Answer 1

I've changed the code for the additem function to this but it only works to an extent now:-
private function addItem():void
// Add item from source Array to Array Collection
if (myDP.length < dpArr.length && !myDP.contains(dpArr[myDP.length])){
     myDP.addItemAt(dpArr[myDP.length],myDP.length);
It does only allow 1 of only the 5 profiles from the array to be added to the tilelist as I wanted but it appears that it is now impossible to add buttons anymore in certain situations.
For example if i run the application add all the profile buttons so all profile buttons are shown in the tile list and then remove profile buttons 2 3 and 4 and then click the add item button 3 times buttons 2 3 and 4 should be added however only 3 and 4 appear after profile 5 and 2 doesn't appear no matter how many times I click 'add item'.
What I want is for all 5 buttons from the array to be addable at any time but only one of each number should be shown. This may be to do with other code but I'm not sure.