[Aristarh Dark]

Код:

procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
begin
  if not(Key in ['0'..'9',Chr(8)]) then
    Key:=#0;
end;

а потом:

Код:

var
  MyNumber:WORD;
begin
  MyNumber:=IntToStr(Edit1.Text);
end;