unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

type
  TMR = record
    P1: string;
    P2: string;
    P3: string;
    P4: string;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure MyProc(AA: TMR);
type
  TMyRec = record
    P1: string;
    P2: string;
    P3: string;
    P4: string;
  end;
var
  AAA: TMyRec;
begin
  AAA.P1 := '1';
  AAA.P2 := '2';
  AAA.P3 := '3';
  AAA.P4 := '4';
  if AA.P1 <> '' then AAA.P1 := AA.P1;
  if AA.P2 <> '' then AAA.P2 := AA.P2;
  if AA.P3 <> '' then AAA.P3 := AA.P3;
  if AA.P4 <> '' then AAA.P4 := AA.P4;
  ShowMessage(AAA.P1 + ' ' + AAA.P2 + ' ' + AAA.P3 + ' ' + AAA.P4);
end;

procedure TForm1.FormCreate(Sender: TObject);
var
  A: TMR;
begin
  MyProc(A);
  A.P1 := '10';
  MyProc(A);
  A.P2 := 'q';
  A.P4 := 'w';
  MyProc(A);
end;

end.