var result = showModalDialog("b2.htm","dialogWidth:270px;dialogHeight:140px;status:'no'"); 
window.returnValue=”aaa” //返回aaa,可直接从表单里获取数据如document.all.textfield.value;
 window.close();           //关闭模态窗口

------解决方案--------------------

弹出模态对话框窗体，弹出子页面
HTML code
#  function openWindow(divIndex) {  
         var width = 550;  
         var height = 450;  
         var url = "child.aspx?divIndex=" + divIndex;  
         var returnVal;  
         returnVal = window.showModalDialog(url, window, 'dialogWidth=' + width + 'px;dialogHeight=' + height + 'px;resizable=no;help=no;center=yes;status=no;scroll=no;edge=sunken');                  
         if (returnVal)  //当直接点模态窗体的X关闭的时候不刷新主页面  
         {// jquery局部更新  
             $("#content div").eq(divIndex).load("AdminColumnHandler.ashx?" + returnVal + "&randomFlag=" +Math.random());  
         }  
     }