I have a Delphi 2007 TRichEdit with several lines in it. I want to scroll the richedit vertically such that a specific line number if approximately centered in the visible/display area of the richedit. For example, I want to write the code for CenterLineInRichEdit in this example:

procedure CenterLineInRichEdit(Edit: TRichEdit; LineNum: Integer);
begin
  ...
  Edit.ScrollTo(...);
end;

procedure TForm1.FormCreate(Sender: TObject);
var
  REdit: TRichEdit;
  i: Integer;
begin
  REdit := TRichEdit.Create(Self);
  REdit.Parent := Self;
  Redit.ScrollBars := ssVertical;
  REdit.SetBounds(10, 10, 200, 150);
  for i := 1 to 25 do
    REdit.Lines.Add('This is line number ' + IntToStr(i));
  CenterLineInRichEdit(REdit, 13);
end;

I looked into using the WM_VSCROLL message, and it allows scrolling up/down one line, etc. but not scrolling to center a specific line. I assume I would need to calculate the line height, the display area height, etc? Or is there an easier way?