Unless you change folders a LOT, you might try using express tools REDIR. It allows you to change directories from the command line - and I think you can make them relative as well.
Here's AutoDesk's solution for CAD2000
Issue
You want to change absolute xref paths to relative paths in a drawing.
Solution
You can use either of the following methods to change absolute xref paths to relative paths, using AutoCAD® Express Tools software.
Method #1
Use the Express Tools command XPATH:
1. On the Express menu, click File Tools > Edit Xref Path.
Alternatively, enter xpath on the command line.
2. Browse to drawing containing xrefs and click Add.
3. Select all the xrefs whose paths you want to change.
4. Enter ..\<drawing path>\ in the Replace With box.
For example, if the xrefs are in K:\drawings\, enter ..\drawings\ in the Replace With box.
Method #2
Use the Express Tools command REDIR:
1. On the Express menu, click File Tools > Path Substitution.
Alternatively, enter redir on the command line.
2. Specify which attachment types to redirect using the REDIRMODE command.
3. Select the Xref option and clear the other options.
4. At the Enter Old Directory prompt, enter the path to be replaced (for example K:\drawings\).
5. At the Replace <original path> With prompt, enter the relative path you want (for example ..\drawings\).
