SqlCommand INSERT INTO only selected rows by checkbox

Hello guys I have got these SqlCommands which inserts and selects. I need to add to prikaz2 (which inserts) condition it would INSERT INTO only these rows wich were selected by checkbox. I have wondered about this for quiet long time but none of my codes were able to do that. Do you guys would suggest me something? In my opinion I have to add "WHERE" ?

SqlCommand comm = new SqlCommand("Select MAX (ID_K) FROM klient", spojeni);
            spojeni.Open();
            int max = (int)comm.ExecuteScalar();
            spojeni.Close();
            for (int i = 0; i < dtg_ksluzby.Rows.Count; i++)
            {
                SqlCommand prikaz2 = new SqlCommand("INSERT INTO klisluz(text,pocet,akce,subkey) values(@val1,@val2,@val3,@val4) ", spojeni); // here I need to add condition to INSERT INTO only selected rows
                prikaz2.Parameters.AddWithValue("@val1", dtg_ksluzby.Rows[i].Cells["text"].Value);
                prikaz2.Parameters.AddWithValue("@val2", dtg_ksluzby.Rows[i].Cells["pocet"].Value);
                prikaz2.Parameters.AddWithValue("@val3", dtg_ksluzby.Rows[i].Cells["akce"].Value);
                prikaz2.Parameters.AddWithValue("@val4", max + 1);                     spojeni.Open();
                prikaz2.ExecuteNonQuery();
                spojeni.Close();
  } 

This is my code for selecting row

private void dtg_ksluzby_CellValueChanged(object sender,
                                   DataGridViewCellEventArgs e)
     foreach (DataGridViewRow row in dtg_ksluzby.Rows)
     {
         DataGridViewCheckBoxCell chk1 = row.Cells[3] as DataGridViewCheckBoxCell;
         if (Convert.ToBoolean(chk1.Value) == true)
         {
             MessageBox.Show("Služba byla vybrána");
         }
         else
         {
         }
     }