java - Unable to call a function within a function with a FB reference

Question

I am trying to get the username from Facebook, I have most of the code however I am not getting data back from the function. The two codes need to be separated so I can call the username in flash (this code is working fine) just need to pass the "username" from the JavaScript.

FB.api('/me?fields=username', function FB(FBusername) { 
    UserName = FBusername.username});


function returndata(){
    FB(FBusername);
    get = UserName
    return get


 };