Cannot find implementation of method ComboBox3Change.

I apologize for the confusion. It seems that there was an error in the code I provided. The message suggests that the implementation of the `ComboBoxChange` method is missing.

To fix this issue, you need to implement the `ComboBox3Change` method in your Delphi code. Here's an updated example that includes the implementation of the `ComboBox3Change` method:

procedure TForm1.ComboBox3Change(Sender: TObject);
var
  ConnectionString: string;
  ADOConnection1: TADOConnection;
  ADOTable1: TADOTable;
begin
  // Construct the connection string
  ConnectionString := Edit1.Text; // Assume the connection string is entered in an Edit control

  // Create the ADO connection component
  ADOConnection1 := TADOConnection.Create(Self);
  try
    // Set the connection string
    ADOConnection1.ConnectionString := ConnectionString;

    // Connect to the database
    ADOConnection1.Connected := True;

    // Create the ADOTable component
    ADOTable1 := TADOTable.Create(Self);
    ADOTable1.Connection := ADOConnection1;

    // Set the table name based on the selected value in ComboBox3
    ADOTable1.TableName := ComboBox3.Text; // ComboBox3 is used to select the table name

    // Open the table
    ADOTable1.Open;

    // Show fields and data in the DBGrid component
    DBGrid1.DataSource := DataSource1;
    DataSource1.DataSet := ADOTable1;

  except
    on E: Exception do
      ShowMessage('Error connecting to the database: ' + E.Message);
  end;
end;

Make sure to replace `ComboBox3` with the actual name of your ComboBox control.

I apologize for the oversight in my previous response. I hope this helps to resolve the issue. If you have any further questions, please let me know.