RadToolTipManager, dynamic tooltip issue.

I have used Telerik controls with asp.net in my project . I am facing a problem with displaying Tooltip. In order to display tooltip, I have used Telerik RadToolTipManager control in .net pages and in RadToolTipManager  - "OnClientBeforeShow" event, calling the bellow given javascript funtion. It working fine for  resolution like "1366 x 768",  but if i change the resolution, Tooltip is breaking. I need to have dynamic tooltip  which will resize according to data it is populated. And please suggest how to adjust font size of text in a Tooltip.

functionOnClientBeforeShow(sender, args){
    setTimeout(function(){var active =Telerik.Web.UI.RadToolTip.getCurrent();var browserWidth =$telerik.$(window).width();var browserHeight =$telerik.$(window).height();var width =(Math.ceil(browserWidth *50/100));
       active.set_width(width);
       active.get_popupElement().style.width = width +"px";},0);}

Any suggestions will be helpful, but need to use RadToolTipManager.

Thanks.