The RTD implementation of object handles uses Excel's RTD mechanism. An add-in that uses the RTD handle implementation therefore has some runtime requirements on any machine where it is to be used.
The model uses a COM module (RtdHandleServer.dll) to support Excel's RTD mechanism. You should register the RTD server module RtdHandleServer.dll, in one of the following ways:
REGSVR32 "C:\Program Files\Planatech\XllPlus\6.0\VS9.0\bin\RtdHandleServer.dll"
Note: The RtdHandleServer DLL is automatically registered when you install the XLL+ toolkit on a development machine. You only need to register it yourself when you deploy XLLs with RTD object handles to another machine.
If you are unable to satisfy these requirements, you can consider using an alternative object handle mechanism. See Other handle implementations for details.