function doClick(buttonName)
{
    var key;
    var e = 'event'
     if(window.event)
          key = window.event.keyCode;     //IE
     else
          key = e.which;     //firefox    
    if (key == 13)
    {	
        var btn = document.getElementById(buttonName);
        if (btn != null)
        { 
            btn.click();
            event.keyCode = 0
        }
    }
}