Addressing the website folder on "PortableApps" disk

For one of the websites I maintain, I keep the copy of the files on my USB Key. Things work well when I edit the files (typically with Notepad Plus), but I come to a minor annoyance when I want to upload the files. On my home computer, the path is "M:\Documents\Folder\my_files", whereas on my office computer it is "I:\Documents\Folder\my_files".

In both cases, M or I is the letter given to my USB key, which is the same drive where PortableApps.com applications are installed.

Is there a way I can address the path in a "standard" way such as "PortableApps\Documents\Folder\my_files"? Or any other trick I may use, at least for those two computers?