Hey Simon, let's bring this back public now...

The file setup works fine if a user copies the workbook and takes it home. It can't find the addin, so bails out, giving the user a message. It also works nicely on the network when you open the workbook. It installs the addin and regsiters it for future use.

The issue is caused in the following situation:
-User connects to the network and successfully registers the addin
-User disconnects from the network
-User opens Excel and gets a nice little message that the xla cannot be found.

Being that they have users with latops that are transient, this is definately an issue. We don't really want to a) tell the users where the addin is, or b) cause an error to occur on the users machine.

Excel doesn't have any built in way to remove an addin from the collection, although I think it could be unloaded. The question is what to do here. I haven't played with the following situation to test it yet:
-Load and register the addin
-Uncheck the addin
-Remove the addin from the system (leaving it registered)
-Try and trap an error if the user opens the workbook remotely.

I'm hypotesizing that it may be best to, upon any workbook close, check if any of the files are open, and if not, uninstall the addin. It will be reinstalled via the workbook next time one is opened. The issue, of course, is the "BeforeClose" portion could be triggered then cancelled.

Thoughts, anyone?