How to fill empty cells of one Microsoft Access database using C#

Thanks for showing me the query logic. That will prove useful in the future. I ended up using a two ValuePair dictionary.

//create ValuePair structure
        struct ValuePair
        {
            public string Lat_Y;
            public string Lon_X;
        }

//create dictionary using ValuePair structure
        Dictionary<string, ValuePair> dictionary = new Dictionary<string, ValuePair>();

//read large parent database that has all cells filled and load dictionary
        private void btnDictionaryTest_Click(object sender, EventArgs e)
        {
            string strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + "D:" + "AccessDatabase.mdb";
            using (OleDbConnection connection = new OleDbConnection(strConn))
            {
                string strOleDb = "Select MTRS, Latitude, Longitude from tblRowMap";
                OleDbCommand command = new OleDbCommand(strOleDb, connection);

                connection.Open();
                OleDbDataReader reader = command.ExecuteReader();

                while (reader.Read())
                {
                    string mTRS = reader.GetString(0);
                    string lat_Y = reader.GetValue(1).ToString();
                    string lon_X = reader.GetValue(2).ToString();
                    dictionary.Add(mTRS, new ValuePair { Lat_Y = lat_Y, Lon_X = lon_X });
                }
                reader.Close();
            }
//read smaller child database that has empty cells that need filling (I used a DataGridView) and
//retrieve values for these keys
              if (dictionary.ContainsKey(mTRS) == true)
            {
                  string latGrid2 = dictionary[mtrsGrid2].Lat_Y.ToString();
                  string lonGrid2 = dictionary[mtrsGrid2].Lon_X.ToString();                
             }
//INSERT these and other required fields into third empty database