I am learning Delphi and I have some problem that I can't solve. When I try to us the ToggleCase function Delphi reports error "Undeclared Identifire". When I use LowerCase or UpperCase everything is normal.
procedure TForm1.Button1Click(Sender: TObject);
Var String;
begin
S:= 'Luka DjUkOviC';
Label1.Caption:= ToggleCase(S);
end;

end. And it doesn't work. I use Delphi 7.