Flex SkinnableContainer skin access Group inside contentGroup

Question

I have skin class in which I defined a Group inside my contentGroup:
<s:Group id="contentGroup" left="0" right="0" top="0" bottom="0" minWidth="475" minHeight="0">
    <s:layout>
                                  <s:HorizontalLayout paddingLeft="0" paddingRight="0" paddingTop="0" paddingBottom="0" gap="2" />
                        </s:layout>
    <s:Group id="group_nav_custom_comp_hgroup_prevnext" left="0" right="0" top="0" bottom="0" minWidth="100" minHeight="0">
                                  <s:layout>
                                            <s:HorizontalLayout paddingLeft="0" paddingRight="0" paddingTop="0" paddingBottom="0" gap="5" />
                                  </s:layout>
                                       <s:Button label="Test Button"/>
                        </s:Group>
</s:Group>
Now, in my CustomComponent that extends the skin class above I am trying to access the "group_nav_custom_comp_hgroup_prevnext" (which is the child group inside the contentGroup) so I can add elements to it at runtime:
  public class GroupNavCustomContainer extends SkinnableContainer
                        private var m_group_prev_next:Group = null;
                        private var m_bAdded_btns:Boolean = true;
                        private var _prevbtn:UIComponent = null;
                        public function GroupNavCustomContainer()
                                  super();
                                  setStyle("skinClass", GroupNavCustomSkin);
                        public function set prevBtn(ui_comp_prev:UIComponent):void
                            if(m_group_prev_next)
                                            _prevbtn = ui_comp_prev;
                                            m_bAdded_btns = true;
                                            invalidateProperties();
                        override protected function partAdded(partName:String, instance:Object):void
                                  trace("In partAdded");
                                  if(partName == "contentGroup")
                                            var group:Group = instance as Group;
                                            var visualElem:IVisualElement = group.getElementAt(0);
                                            m_group_prev_next = visualElem as Group;
                                  super.partAdded(partName, instance);
                        override protected function commitProperties():void
                                  super.commitProperties();
                                  if (m_bAdded_btns)
                                            m_bAdded_btns = false;
                                            m_group_prev_next.addElement(_prevbtn);
The result is my: group_nav_custom_comp_hgroup_prevnext is just not showing up at all, evidenced by the fact that the button present in it at compile time is not visible. Anyone know how to get it to show up?    - thx in advance -Mike

Answer 1

Based on Nikos tip, I rearranged my code and added 'group_nav_custom_comp_hgroup_prevnext' as a SkinPart, so now I have access to it, in other functions of the class, but still I do not see the button inside that nested group showing up. 
@ drkstr_1 :  Are you saying I cannot have a group inside my contentGroup? if so if then how can I have a group appear right next to it? --- do I have to add it programmatically in the  parent component -- but doesn't that defeat the purpose of the skin?
thx - Mike
package com.viiv.digi.views.navigation
          import mx.core.IVisualElement;
          import mx.core.UIComponent;
          import skins.GroupNavCustomSkin;
          import spark.components.Group;
          import spark.components.SkinnableContainer;
          public class GroupNavCustomContainer extends SkinnableContainer
                    private var m_group_prev_next:Group = null;
                    private var m_bAdded_btns:Boolean = false;
                    private var _prevbtn:UIComponent = null;
                    [SkinPart(required="true")]
                    public var group_nav_custom_comp_hgroup_prevnext:Group;
                    public function GroupNavCustomContainer()
                              super();
                              setStyle("skinClass", GroupNavCustomSkin);
                    public function set prevBtn(ui_comp_prev:UIComponent):void
                        _prevbtn = ui_comp_prev;
                              m_bAdded_btns = true;
                              invalidateProperties();
                    public function get prevBtn():UIComponent
                              return _prevbtn;
                    override protected function partAdded(partName:String, instance:Object):void
  trace("In partAdded");
                              super.partAdded(partName, instance);
                    override protected function commitProperties():void
                              super.commitProperties();
                              if (m_bAdded_btns)
                                        m_bAdded_btns = false;
                                        group_nav_custom_comp_hgroup_prevnext.addElement(_prevbtn);