showModalDialog关闭后进if(!Page.IsPostBack)

<input id="btn_add" class="btn" type="button" value="新增" onclick="javascript:add_open_new();" />

function add_open_new()
         {
            var mywin = window.showModalDialog('edti_jobsecqbinfo.aspx?insert=0&jobcqbID=1','','status:Modeless;edge:raised;unadorned:no;scroll=no;resizable:yes;center=yes;help:no;dialogwidth:510px;dialogheight:380px;');
            
            if(mywin == 'refresh')
            {
                //return true;//刷新但进不了if(!IsPostBack){}
                document.getElementById("a_refresh").click();
            }
            else
            {
                return false;
            }
         }

 <a href="sel_job_cq.aspx?jobseid=<%=id%>" id="a_refresh" runat="server" style="display:none;"></a><!--for if (!IsPostBack)-->