procedure TForm1.EnterPrimerClick(Sender: TObject);
begin
 Primes.Edit;
end;

procedure TForm1.SaveChangesClick(Sender: TObject);
var
 IsPrime: Boolean;
 Count: Integer;
 NumToTest: Integer;
begin
 IsPrime := True;
 Count := 2;
 NumToTest := StrToInt(EntPrime.Text);
  while (Count < NumToTest) and (IsPrime) do
  begin
   {czy liczba jest liczb pierwsz ?}
   if NumToTest mod Count = 0 then IsPrime := False;
   inc(Count);
  end;

  if IsPrime then
   Primes.Post
  else
   begin
    Application.MessageBox('To nie jest liczba pierwsza!','Uwaga',MB_OK);
    Primes.Cancel;
   end;
end;