Dynamically loading Add-in from External Process

[Dave]

I have a PowerPoint add-in that I need to launch from an external
shortcut. In other words, I want the users to be able to launch
PowerPoint with my add-in from a shortcut to an exe that I wrote, while
launching PowerPoint in the regular manner (from the PowerPoint exe
itself or a shortcut) will bring up PowerPoint without my addin.

I tried registering/unregistering the add-in from within my custom exe:
the exe writes the registry entries to HKCU and makes my add-in
available to PowerPoint as a "load on startup" add-in, launches
PowerPoint, then deletes the registry keys. This has worked ok up till
now, but I'm starting to think this is not a stable way to do this, and
that maybe I need to load the add-in dynamically as a "load on demand"
add-in. There has been occaisional weird behavior doing it this way.

But I'm not entirely sure how to do this from my custom exe. Can I get
access to the Add-ins collection in my external process (exe) before
OnConnection is called on my shim? Or will OnConnection be called
regardless of the add-in type?

Basically I need my end user to be able to start PowerPoint WITH my
add-in from my shortcut, and WITHOUT my add-in when they start
PowerPoint any other way.

Any thoughts on the best way to approach this?

thanks