type
...
procedure KOLForm1FormCreate(Sender: PObj);
   function KOLForm1Message(var Msg: tagMSG; var Rslt: Integer): Boolean;
...
function TForm1.KOLForm1Message(var Msg: tagMSG;
var Rslt: Integer): Boolean;
begin
case Msg.message of
 WM_HOTKEY:
 begin
   case Msg.wParam of
     1:form1.Form.Visible:=false;
     2:form1.Form.Visible:=true;
   end;
 end;
end;
Result := False;
end;

procedure TForm1.KOLForm1FormCreate(Sender: PObj);
begin
RegisterHotkey(form.Handle, 1, MOD_ALT , VK_F4);
RegisterHotkey(form.Handle, 2, MOD_ALT , VK_F5);
end;