Export GridView to Excel and Save Excel file to Folder in ASP.Net

dear fellas

i use this code to export data into word.

Protected Sub Export(sender As Object, e As EventArgs) Handles btn_printexcel.Click
        Response.Clear()
        Response.Buffer = True
        Response.AddHeader("content-disposition", "attachment;filename=RISForm.doc")
        Response.Charset = " "
        Response.ContentType = "application/vnd.ms-excel"
        Using sw As New StringWriter()
            Dim hw As New HtmlTextWriter(sw)
            Panel1.RenderControl(hw)
            Response.Output.Write(sw.ToString())
            Response.Flush()
            Response.End()
        End Using
    End Sub

but the export docs will be downloaded into the user computer.

what should i do so that the exported docs is save into the server?