Undeclared identifier: 'YH' &Undeclared identifier: 'QX'怎么办

procedure TEnter.Enter_BtnClick(Sender: TObject);
var
  Password:string;
begin
   if XM_CB.Text='' then
    begin
      MessageBox(handle,'用户名不能为空，请选择或输入用户名！','错误',MB_OK or MB_ICONERROR);
      exit;
    end;
  DL_ADOQ.Close;
  DL_ADOQ.SQL.Clear;
  DL_ADOQ.SQL.Add('Select Password,QXID From YH Where UserName=(:Name)');
  DL_ADOQ.Parameters.ParamByName('Name').Value:=XM_CB.Text;
  DL_ADOQ.Open;
  if DL_ADOQ.FieldByName('Password').IsNull then Password:=''
  else Password:=DL_ADOQ.FieldValues['Password'];
  if Password=MM_E.Text then
    begin
      YH:=XM_CB.Text;
      QX:=DL_ADOQ.FieldValues['QXID'];
      self.Hide;
      DL_ADOQ.Close;
      FreeAndNil(DL_ADOQ);
      with TMain.Create(nil) do
        try
          ShowModal;
        finally
          Free;
          Application.Terminate;
        end;
      end
    else begin
      MessageBox(0,'密码错误请重新输入！','密码错误',MB_OK or MB_ICONERROR);
      MM_E.Text:='';
    end;
end;提示：[错误] Enter_Form.pas(64): Undeclared identifier: 'YH'
     [错误] Enter_Form.pas(65): Undeclared identifier: 'QX'
     [致命错误] TKSCXT.dpr(7): Could not compile used unit 'Enter_Form.pas'
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