Nemt ? om global variabel

Lig den på din klasse

Du kan oprette din DataStream som en property på din form.
******************
unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
    FDataStream : TMemoryStream;
  public
    { Public declarations }
    property DataStream : TMemoryStream read FDataStream write FDataStream;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
  DataStream := TMemoryStream.Create;
  DataStream.Position := 0;
end;

end.
*************
unit Unit2;

interface

uses unit1;

implementation

procedure Test;
begin
  Form1.DataStream.Position := 0;
end;


end.