how to validate textinput within itemrenderer?

I have textinput within list itemrenderer like

main.mxml

    开发者_如何学JAVA    <s:List
        id="videoAttachmentsList"  
        itemRenderer.normalView="com.engage.discussion.attachment.renderers.VideoAttachmentRenderer"
        >
 <mx:button  label="add"  click=addevent(Event) />

VideoAttachmentRenderer.as

 <TextInput  styleName="commonTextInput" 
                  prompt="Enter a video header"
                  id="headerText"
                  x="75" width="185" height="21"
                  bottom="5"
                  fontSize="10"
                  maxChars="30"/>
<fx:Declarations>
        <mx:StringValidator source="{headerText}" property="text" required="true" maxLength="30" requiredFieldError="Please enter video header"/>
    </fx:Declarations>

My doubts is when i click add button on (main.mxml) that time need validate headerText(Textinput)(VideoAttachmentRenderer.as) . is it possible to validate string withing itemRenderer. could u give any guidance ?

override the set data method and trigger the validation in there