how to save Ajax CalendarExtender value in a textbox.text

[sheringkapoting]

Frnds, I have a textbox txtSalaryMonth which displays the value of Ajax CalenderExtender on click of a Image. But when I press Another button btnOK to send the calendarVale as paramenter to Database.. It shows txtSalaryMonth.text as null... My txtSalaryMonth.Readonly = false. My Code is:

and Java Script is :

    function onCalendarSalShown() 
    {
        var cal = $find("calendar1");
        //Setting the default mode to month
        cal.\_switchMode("months", true);
        //Iterate every month Item and attach click event to it
        if (cal.\_monthsBody) 
        {
            for (var i = 0; i < cal.\_monthsBody.rows.length; i++) 
            {
                var row = cal.\_monthsBody.rows\[i\];
                for (var j = 0; j < row.cells.length; j++) 
                {
                    Sys.UI.DomEvent.addHandler(row.cells\[j\].firstChild, "click", callSal);
                }
            }
        }
    }

    function onCalendarSalHidden()
     {
        var cal = $find("calendar1");
        //Iterate every month Item and remove click event from it
        if (cal.\_monthsBody) 
        {
            for (var i = 0; i < cal.\_monthsBody.rows.length; i++) 
            {
                var row = cal.\_monthsBody.rows\[i\];
                for (var j = 0; j < row.cells.length; j++) 
                {
                    Sys.UI.DomEvent.removeHandler(row.cells\[j\].firstChild, "click", callSal);
                }
            }
        }
    }

    function callSal(eventElement) 
    {
        var target = eventElement.target;
        switch (target.mode) 
        {
            case "month":
                var cal = $find("calendar1");
                cal.\_visibleDate = target.date;
                cal.set\_selectedDate(target.date);
                cal.\_switchMonth(target.date);
                cal.\_blur.post(true);
                cal.raiseDateSelectionChanged();
                break;
        }
    }

plss Help