I was unable to remove the "Missing" reference on my new machine which did
not have the 3rd party product installed. The "Missing" references
indirectly caused "cannot find project or library" errors elsewhere in my VB
code. I had to do the following:

- delete the excel workbook and addins from my new machine.

- go back to my original machine which had the 3rd party sw installed.
- remove all references in my VB code to the 3rd party sw.
- remove the VB - Tools reference to the 3rd party sw.
- remove the 3rd party addin.

- make another copy of my workbook and addins on my original machine.
- install the new copy on my new machine.
- the excel workbook and addins now work on my new machine now works.