function CheckFile(var UserFile: TextFile; Size: Integer; Path: String): boolean;
var
    I, Value: Integer;
    IsCorrect: Boolean;
begin
    AssignFile(UserFile, Path);
    Reset(UserFile);
    IsCorrect := True;
    I := 0;
    while not(SeekEoLn(UserFile)) and IsCorrect do
    Begin
        Try
            Read(UserFile, Value);
        except
            IsCorrect := False;
        End;
        Inc(I);
    End;

    if I<>Size then
        IsCorrect := False;

    CloseFile(UserFile);
    CheckFile := IsCorrect;
end;

procedure TForm1.N4Click(Sender: TObject);
var
    I, Size: Integer;
    UserFile: TextFile;
    Value: Integer;
    Path: String;
begin
    Size := SpinEditMas.Value;
    Path := OpenDialog1.FileName;
    if OpenDialog1.Execute then
    Begin
        if CheckFile(UserFile, Size, Path) then
        begin
            AssignFile(UserFile, OpenDialog1.FileName);
            Reset(UserFile);
            for I := 0 to SpinEditMas.Value-1 do
                Begin
                    Read(UserFile, Value);
                    StringGrid1.Cells[i, 0] := IntToStr(Value);
                End;
            CloseFile(UserFile)
        end
        else
            MessageDlg('Данные в файле некорректны', mtError, [mbOK], 0)
    End;
    if Length(StringGrid1.Cells[0,0]) > 0 then
        Button2.Enabled := True;
end;