Hi tjh,
Not all application alerts can be suppressed with .DisplayAlerts!

Note that the Add method of the Addins collection supports an option Boolean
argument for the copy. Set it to TRUE or FALSE as desired, to suppress the
prompt.

Also note that the CopyFile method has an optional Boolean argument to
overwrite an existing file with the same name. Setting this to TRUE will
simply copy the file (replacing any existing one with the same name).

<FWIW If you're just looking for a simple way to update users' addins, I
suggest you use the same filename and put version/release info in its Summary
Properties. This will display in the tooltip in explorer windows. If the
addin is already installed, the next time Excel is opened it will look for
the same filename but get the new version you just put in the source folder.
...No need here to re-install it!

The message you say you're getting indicates that Excel is attempting to
copy the file to the user's addins folder. I think it would be better to
store it in its own folder under "Program Files" if on a local machine. If
it's stored on a network drive, any user-accessible location for its folder
will do. When asked if you want to copy it to the user's addin folder, say NO
to this prompt because:
1. You want all users on the network referencing the same file from the
server location. This makes maintenance easier for you because there's only
one file to update.
2. You want the same addin available to all users of a local machine (I
would think).

Note that you can overwrite an addin file at any time, but it won't be
current for your users until their copy of Excel is re-opened.

As for distribution:
I'm not sure why you're trying to install it programmatically, but using
TOOLS, ADD-INS, BROWSE... will get it done even for the most novice user.
Putting a simple instruction in a text file would be equally effective, and
it's one less addin for you to maintain. Alternatively, for your updates, a
Winzip Self-Extracting file works nice for stand-alone machines.

HTH
Regards,
Garry