Topic: how is an external function registered with SWFupload

In xajax.inc.php I don't see a way to register a function with SWFupload where the function is in an included file.  As I read the inline documentation for the xajax->register() function in xajax.inc.php, $mArg can be EITHER $sIncludeFile OR $aCallOptions OR $sEventHandler, meaning I could pass the function either an include path OR the call options for SWFupload.
[code=PHP]
$xajax->register(
    XAJAX_FUNCTION,
    "myFunction",
    array("mode" => "'SWFupload'", "SWFform" => "upload_form")
);
[/code]
So I tried to pass in "myFunction" as an array:
[code=PHP]
$xajax->register(
    XAJAX_FUNCTION,
    "rray("myFunction", "includePath"),
    array("mode" => "'SWFupload'", "SWFform" => "upload_form")
);
[/code]
Does anyone have an idea how this should (or can) be done?