I tried the code as listed above and found it to perform as follows:
It prompts me to chose the main document.
I select the location and file and the macro begins processing the data
It finds all acronyms that are not listed in the Acronym document.

It appears to check all the acronyms that are not used within the main document BUT fails to delete them from the table (it actually lists them as occurring 1 time in the document)

It also does not close out the main document when it is finished. It also does not permit you to close it out manually. I have to use the task manager to get it to close out. <-- Disregard.