AddIn Default Path - Moving Spreadsheed between Users/Computers

When moving a spreadsheet between two users on two different PCs the cells
containing any AddIn functions get changed/modified preventing seemless
operation.

Steps:
1. A spreadsheet is created with cells which call out a functions contained
in AddIn
2. The spreadsheet is saved, and when re-opened on the same PC all is Ok!
3. Spreadsheet is opened by another user on a different PC, a message is
display stating an invalid path exists on the AddIn links
4. Regardless of if I use the default paths or force a path (say
"C:\AddIn") the message always comes up when the spreadsheet has been saved
on one PC then moved to another.

How can this be configured to be seemless when passing a file between
several users

Thanks in advance,
John