$(document).ready(function(){



    // Global function (will be include in any HTML file)

    function m3_result(size_1, size_2, size_3){

        $.get('http://www.google.com', function(data){

            return data;

        });

    }   



    // Another function

    function calculate(){

        var size_1 = parseFloat($('#add_document_form #size_1').val());

        var size_2 = parseFloat($('#add_document_form #size_2').val());

        var size_3 = parseFloat($('#add_document_form #size_3').val());          

        var ax = m3_result(size_1, size_2, size_3);



        alert(ax); // Here ax return: UNDEFINED  

    }



    // Run

    calculate();

});

Results are undefined, but I would like that calculate() will wait for m3_result() to execute. I see that here problem is coming when I added $.get(), but its needed...

I have searching for callback() like functions, but none fit to my needs, or I just didnt put that right.
Any help will be highly appreciated, thanks.

GET url will be localy and element IDs are also ok.