Protected Sub GridView1_RowCommand(ByVal sender As Object, ByVal e As GridViewCommandEventArgs) Handles GridView1.RowCommand

        If GridView1.Rows.Count - 1 > 0 Then

            If e.CommandName = "WHATEVERYOURBUTTONCOMMANDNAME" Then

 Dim CompanyID As String = GridView1.DataKeys(Convert.ToString(e.CommandArgument)).Item(0).ToString

Session.Add("CompanyID", CompanyID)

               Response.Write("<script>")
                Response.Write("window.open(YOURDETAILSWINDOW.aspx','_blank','toolbar=0,location=0,menubar=0,resizable=0,width=400,height=320')")
                Response.Write("</script>")

end if

end if