How to open a popup in Iframe according to scrol position of browser window?

hi all,
i have a problem i am trying to open a pop up in Iframe window. i am able to opne it in center of iframe window but i wants to open it according to the scrol position of browser window.
I m using the following jquery plugin code:

function getScrollXY() {
            var scrOfX = 0, scrOfY = 0;
            if (typeof (window.pageYOffset) == 'number') {
                //Netscape compliant 
                scrOfY = window.pageYOffset;
                scrOfX = window.pageXOffset;
            } else if (document.body && (document.body.scrollLeft || document.body.scrollTop)) {
                //DOM compliant 
                scrOfY = document.body.scrollTop;
                scrOfX = document.body.scrollLeft;
            } else if (document.documentElement && (document.documentElement.scrollLeft || document.documentElement.scrollTop)) {
                //IE6 standards compliant mode 
                scrOfY = document.documentElement.scrollTop;
                scrOfX = document.documentElement.scrollLeft;
            }
            return { X: scrOfX, Y: scrOfY };
        }

        function getWindowSize() {

            var myWidth = 0, myHeight = 0;
            if (typeof (window.innerWidth) == 'number') {
                //Non-IE 
                myWidth = window.innerWidth;
                myHeight = window.innerHeight;
            } else if (document.documentElement && (document.documentElement.clientWidth || document.documentElement.clientHeight)) {
                //IE 6+ in 'standards compliant mode' 
                myWidth = document.documentElement.clientWidth;
                myHeight = document.documentElement.clientHeight;
            } else if (document.body && (document.body.clientWidth || document.body.clientHeight)) {
                //IE 4 compatible 
                myWidth = document.body.clientWidth;
                myHeight = document.body.clientHeight;
            }
            return { X: myWidth, Y: myHeight }
        }

        function centerPopup4(vall) {
            var windowDim = getWindowSize();
            var popupHeight = jQuery("#FeedBox").height();
            var popupWidth = jQuery("#FeedBox").width();
            var scroll = getScrollXY();
            jQuery("#" + vall).css({
                "position": "absolute",
                "top": windowDim.Y / 2 - popupHeight / 2 + scroll.Y - 15,
                "left": windowDim.X / 2 - popupWidth / 2 + scroll.X - 15
            });
            //only need force for IE6

            jQuery("#FeedBox")..show()
               
        }

Help me to solve my problem..
regards dsingh