How can I UpdatePanel.Update() during processing

Follow the code test.I'm trying to show each line per time... but this 5 lines were showed after the proc ended

How can I do this ?

For iAsInteger = 1To 5
Dim drAs DataRow = Session("dt").Rows.Add
dr("DLLFilename") =CStr(i * 1)
dr("DLLDatetime") =CStr(i * 2)
dr("PackageName") =CStr(i * 3)
dr("PackageID") =CStr(i * 4)
dr("DLLFolder") =CStr(i * 5)
dr("MSIFolder") =CStr(i * 6)

GridView1.DataSource =New DataView(Session("dt"))
GridView1.DataBind()
UpdatePanel1.Update()

System.Threading.Thread.Sleep(1000)
Next

The data is only sent to the browser when the server method completes. Calling Update() only flags the updatepanel to be updated when the server processing is complete.