procedure TForm1.FormCreate(Sender: TObject);
var used: array [0..9] of boolean;
    i,t:shortint;
    int: integer;
begin
    Randomize();
    for i:=0 to 9 do
       used[i]:=false;

    t:=1+Random(9);
    int:=0;
    for i:=1 to 4 do begin
       while (used[t]) do
          t:=Random(10);
       used[t]:=true;
       int:=int*10+t;
    end;
    ShowMessage(IntToStr(int));

end;