Значение DBLookupComboBox

Я думаю что у меня есть то, что вы хотите. Если вы обратитесь к свойству LookUpValue, то вы получите поле, которое .... ищете.

Я надеюсь что помог вам.

unit clookup;

interface

uses
  SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
  Forms, Dialogs, StdCtrls, DB, DBLookup;

type
  TDBJustLookupCombo = class(TDBLookupCombo)
  private
    { Private declarations }
  protected
    { Protected declarations }
    function GetLValue: TField;
  public
    { Public declarations }
    property LookUpValue: TField read GetLValue;
  published
    { Published declarations }
  end;

  TDBJustLookupList = class(TDBLookupList)
  private
    { Private declarations }
  protected
    { Protected declarations }
    function GetLValue: TField;
  public
    { Public declarations }
    property LookUpValue: TField read GetLValue;
  published
    { Published declarations }
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('Data Controls', [TDBJustLookupList,
    TDBJustLookupCombo]);
end;

function TDBJustLookupCombo.GetLValue: TField;
begin
  Result := LookupSource.DataSet.FieldByName(LookUpField);
end;

function TDBJustLookupList.GetLValue: TField;
begin
  Result := LookupSource.DataSet.FieldByName(LookUpField);
end;

end.