accessing a variable in mxml file from an action script file

Hi,

    I think this is a very very dumb question but i am nto being able to gigure this out i am a total newbie to flex.

     i have a mxml file e.g. aaa.mxml which has the following declaration

     ........ //some lines of code

     <mx:XMLListCollection

id="listCollectionData" source="{srv_new.lastResult.data.result}" />

  Now if i have some external file e.g. myActionScript.as - how do i access the listCollectionData value defined in aaa.mxml file?

Thank you so much ...

Rohit