No doubt there is a better way... but here's how I do it.
1.) Get a list of extensions in question via an export report and open delimited style in Excel. Put the extensions in column B.
2.) In excel column A enter cl am al (clear amw all)and copy it all the way down to the end of the extension list.
3.) In excel column C enter ; and copy it all the way down to the end of the extension list.
4.) Now you have cl am al xxxx ;
5.) Copy all cells top to bottom of all three columns A B C
6.) Open notepad and paste information
7.) In notepad highlight the empty space between cl am all and xxxx and copy it. Then click Edit and Replace. in the Find what field right click and past the empty space that you just copied. in the Replace with field hit the space bar to add a space. then click replace button a couple of times, if it correctly worked on the first line then hit replace all.
8. Now do the same with the "space ;" in the Find what field and replace with ";" replacing with "no space ;".
9. Now its formatted correctly (cl am al xxxx

.. However to use the command stacking technique they need to be one after another (cl am al xxxx;cl am al xxxx

. This is the part that is painful... go to the end of the top entry and hit delete, then hit end, then delete and over and over... ensuring you don't delete a character or alter the format (the report will fail if you do). You can get in a rhythm and stack all the commands fairly quickly.
Wildcard