Help! function not getting called in onLoad

Hello there,

Here is my problem,
I am loading one xml file and onload (or onData) of this file I am calling another function but, this function is not getting called.
What can be the issue? Can delegates be used here and how?

Here is the code for reference

//path for _global.bookXML is defined already.
_global.book_xml = new XML();
_global.book_xml.ignoreWhite = true;

// load content xml
//after content xml is loaded
_global.book_xml.onLoad = function(success)
    if (success)

public function fnCallOtherFunction()
//code for this function

Can any one help with this issue?

Thanks in advance