It is common practice in my office to create Excel spreadsheets using functions from a custom add-in. Every user has a copy of the add-in on their computer. We often encounter the problem where links are introduced into the Excel worksheet, so that the user is prompted to Update Links whenever the file is opened.

Here is how I've recreated the problem. Let's say I create a spreadsheet on my hard drive using a function from the custom add-in. The formula that I enter is 

Please Login or Register  to view this content.
I save the workbook and close it. Then I copy the workbook to a network drive so that my colleagues can access it. Whenever they (or I) open the workbook from the network drive, there is a prompt to update links, and the formula reads

Please Login or Register  to view this content.
Where user-name is my network login name.

How can I prevent this from happening? All of the users who have use this worksheet also have the add-in installed, so I would think that this shouldn't be occurring.