procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
begin
  // Memastikan karakter yang diinput adalah '0'..'9'
  if not (key in[#8,'0'..'9'])then
  begin
    key:=#0;
    beep;
  end;
end;
procedure TForm1.Edit1KeyUp(Sender: TObject; var Key: Word;
  Shift: TShiftState);
var
  s:string;
  i,l:integer;
begin
  // Sisip karakter '.'
  s:=edit1.Text;
  for i:=1 to length(s) do
  begin
    if s[i]='.' then
    begin
      delete(s,i,1);
    end;
  end;
  l:=length(s);
  if (length(s)>3) then
  begin
    for i:=1 to (length(s) div 3) do
    begin
      l:=l-2;
      if l<>1 then
        insert('.',s,l);
      l:=l-1;
    end;
  end;
  edit1.Text:=s;
  edit1.SelStart:=length(edit1.Text);
end;