Update 2nd form from main form

My application produces a set of data that changes over time. I am trying to display this data in a floating dialog box, which is a stayontop toolwindow. Ultimately I will want to display several of these floating windows (3 or 4).

Examples of the code I'm using are as follows:

procedure TForm1.StartButtonClick(Sender: TObject);
begin
  Form2.Show;  {display the floating window....}
  Timer1.Enabled := true;  {off we go....}
end;

procedure TForm1.Timer1Timer(Sender: TObject);
begin
{Evaluate new data....}
  ...
  ...do some stuff...
  ...
{Update TChart on form 2....}
  with Form2.Chart1 do
  begin
    ...
    ...do some stuff...
    ...
  end;
end;


Although the application compiles and run's OK, the dialog box (Form2) is never updated, regardless of whether it, or the main form (Form1) has the focus.
I therefore assume that Form2 never processes messages. I tried showing Form2 as modal, but of course then Form1 didn't respond, presumably for the same reason.

I'm after some advice on the best approach to take. Specific code is not required, although I won't be offended if anyone includes some!

I do not particularly want to run Form2 in its own thread if I can avoid it; I already have several threads running and do not want to add more thread management overhead.
Do I need to force Form2 to process messages or am I doing something really stupid?

Thanks,
   FrankTheRat.