Delegate class - passing params with function


I am wanted to know how can i pass a parameter to the function which I’m calling using Delegate class. I know to pass params having static values such as true / false or a static string “hello”.

var myFunc:Function = btn.onRelease = Delegate.create(tihs, releaseHandler);
myFunc.**str **= "hello";

function releaseHandler()
    trace("my param = " + **arguments.caller.str**); //output: hello 

Here **str **can be retrieved as ‘arguments.caller.str’ inside the function.

But in case i want to pass the reference of the ‘btn’ button. Then how can i do this ?