Hey @Matze,
Okay...
My first thought is that it's really a lot of trouble to fool around with Jim's very complicated macro without need – better to simplify if possible.
The task would be better done with a basic Excel worksheet or better yet with BBEdit and a more simple text table.
I recommend BBEdit because…
- Although BBEdit is a commercial product, the trial version reverts to a
still very powerful and free (BBEdit-Lite) version after 30 days.
- It is very Mac-like.
- It has excellent support for RegEx.
- It is very AppleScriptable.
- It has a two versatile command line tools.
- It has been in continuous development for over 25 years.
A text file is much easier to work with an manage than a spreadsheet, unless of course you're very familiar with the spreadsheet software.

By using BBEdit our data acquisition script becomes this simple:
# Acquire rename table.
tell application "BBEdit"
tell front text window
set renameTable to contents of lines whose contents is not ""
end tell
end tell
set renameTable to items 4 thru -1 of renameTable
Although using a simpler Excel workbook also gives us a much simpler data acquisition script:

# Acquire rename table.
tell application "Microsoft Excel"
tell active sheet of active workbook
set valuePairList to value of used range
end tell
end tell
if item 1 of valuePairList contains "Old File Name" then
set contents of (a reference to item 1 of valuePairList) to 0
end if
set valuePairList to lists of valuePairList
From either one of these places it becomes pretty straightforward to iterate through the old-name ⇢ new-name pairs and rename the files.
I can do either of these pretty easily.
The remaining question for you is where do you want the the target folder to be?
- Do you want the front Finder window?
- Do you want a specific folder path?
- Do you want to pick the folder on the fly?
In general I think it's better to work with the file extension in the rename list, but that's not absolutely necessary.
Some people choose to hide file extensions in the Finder, and that can affect what you copy out of the Finder.
I think this is a bad idea, but YMMV.
Let me know what direction you want to go in.
-Chris