The following example shows how you can create a pop up TitleWindow container using the Flex PopUpButton control
<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/04/13/creating-a-pop-up-titlewindow-using-the-popupbutton-control-in-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout
="vertical"
        verticalAlign
="middle"
        backgroundColor
="white">

    
<mx:Style>
        TitleWindow {
            roundedBottomCorners: false;
            borderColor: haloSilver;
            backgroundColor: haloSilver;
            borderAlpha: 0.8;
            backgroundAlpha: 0.8;
            dropShadowEnabled: false;
        }
    
</mx:Style>

    
<mx:Script>
        
<![CDATA[
            import mx.controls.CheckBox;
            import mx.controls.dataGridClasses.DataGridColumn;

            private function checkBox_change(evt:Event):void {
                var ch:CheckBox = evt.currentTarget as CheckBox;
                var idx:int = int(ch.data);
                var obj:Object = arrColl.getItemAt(idx);
                obj.sel = ch.selected;
                arrColl.disableAutoUpdate();
                arrColl.setItemAt(obj, idx);
            }

            private function selectAll(evt:Event):void {
                var idx:int;
                var item:Object;
                for (idx=0; idx<arrColl.length; idx++) {
                    item = arrColl.getItemAt(idx);
                    item.sel = CheckBox(evt.currentTarget).selected;
                }
                arrColl.refresh();
            }

            private function sel_labelFunc(item:Object, col:DataGridColumn):String {
                var bool:Boolean = item.hasOwnProperty("sel") &&
                            (item.sel == "true" || item.sel == true);
                return bool.toString();
            }
        
]]>
    
</mx:Script>

    
<mx:ArrayCollection id="arrColl">
        
<mx:source>
            
<mx:Array id="arr">
                
<mx:Object label="Button" />
                
<mx:Object label="ButtonBar" />
                
<mx:Object label="CheckBox" />
                
<mx:Object label="ColorPicker" sel="true" />
                
<mx:Object label="ComboBox" sel="true" />
                
<mx:Object label="DataGrid" sel="true" />
                
<mx:Object label="DateChooser" />
                
<mx:Object label="DateField" sel="true" />
                
<mx:Object label="HorizontalList" />
                
<mx:Object label="HRule" />
                
<mx:Object label="HSlider" />
                
<mx:Object label="Image" />
                
<mx:Object label="Label" />
                
<mx:Object label="LinkBar" />
                
<mx:Object label="LinkButton" />
                
<mx:Object label="List" sel="true" />
                
<mx:Object label="Menu" />
                
<mx:Object label="MenuBar" />
                
<mx:Object label="NumericStepper" sel="true" />
                
<mx:Object label="ProgressBar" />
                
<mx:Object label="RadioButton" />
                
<mx:Object label="RadioButtonGroup" />
                
<mx:Object label="RichTextEditor" sel="true" />
                
<mx:Object label="Spacer" />
                
<mx:Object label="SWFLoader" />
                
<mx:Object label="TabBar" />
                
<mx:Object label="Text" />
                
<mx:Object label="TextArea" />
                
<mx:Object label="TextInput" />
                
<mx:Object label="TileList" />
                
<mx:Object label="Tree" sel="true" />
                
<mx:Object label="VideoDisplay" />
                
<mx:Object label="VRule" />
                
<mx:Object label="VScrollBar" />
                
<mx:Object label="VSlider" />
            
</mx:Array>
        
</mx:source>
    
</mx:ArrayCollection>

    
<mx:ApplicationControlBar dock="true">
        
<mx:PopUpButton id="popUpButton"
                label
="Please select some components"
                openAlways
="true"
                close
="arrColl.refresh();">
            
<mx:popUp>
                
<mx:TitleWindow id="titleWin"
                        height
="200"
                        showCloseButton
="true"
                        verticalScrollPolicy
="on"
                        horizontalScrollPolicy
="off"
                        close
="popUpButton.close();">
                    
<mx:ToolBar width="320">
                        
<mx:Repeater id="myRep"
                                dataProvider
="{arrColl}">
                            
<mx:CheckBox data="{myRep.currentIndex}"
                                    label
="{myRep.currentItem.label}"
                                    selected
="{myRep.currentItem.sel}"
                                    change
="checkBox_change(event);"
                                    width
="100" />
                        
</mx:Repeater>
                    
</mx:ToolBar>
                    
<mx:ControlBar>
                        
<mx:CheckBox label="Select All"
                                labelPlacement
="left"
                                change
="selectAll(event);" />
                    
</mx:ControlBar>
                
</mx:TitleWindow>
            
</mx:popUp>
        
</mx:PopUpButton>
    
</mx:ApplicationControlBar>

    
<mx:DataGrid dataProvider="{arrColl}">
        
<mx:columns>
            
<mx:DataGridColumn dataField="label" />
            
<mx:DataGridColumn dataField="sel"
                    labelFunction
="sel_labelFunc" />
        
</mx:columns>
    
</mx:DataGrid>

</mx:Application>