gPopupWin = null; 
function openPopup(sPage, lWidth,lHeight) {
var left = Math.floor( (screen.width - lWidth) / 2);
var top = Math.floor( (screen.height - lHeight) / 2);
var winParms = "scrollbars=1,resizable=0,top=" + top + ",left=" + left + ",height=" + lHeight + ",width=" + lWidth;
    if(!gPopupWin || gPopupWin.closed){
        gPopupWin=window.open(sPage, "gPopupWin", winParms); 
    } else {
        gPopupWin.close();
	gPopupWin=window.open(sPage, "gPopupWin", winParms); 
}
}