Yes, use Cbrine's steps 6 - 8. Where I commented in my code (the green text) is where you need to change that text to the correct module name of wherever you paste this code. Putting this in your Personal.xls file will allow you access to it the entire time you have Excel open. You'll need to do one more thing if this is what you want:
1) Open the VBE (Alt + F11)
2) Select PERSONAL.XLS on the left, expand all folders
3) Double click the ThisWorkbook module, paste this code...
<font face=Tahoma New><SPAN style="color:#00007F">Private</SPAN> <SPAN style="color:#00007F">Sub</SPAN> Workbook_BeforeClose(Cancel <SPAN style="color:#00007F">As</SPAN> <SPAN style="color:#00007F">Boolean</SPAN>)
<SPAN style="color:#00007F">Call</SPAN> ResetRightClick
<SPAN style="color:#00007F">End</SPAN> <SPAN style="color:#00007F">Sub</SPAN>
<SPAN style="color:#00007F">Private</SPAN> <SPAN style="color:#00007F">Sub</SPAN> Workbook_Open()
<SPAN style="color:#00007F">Call</SPAN> AppendRightClick
<SPAN style="color:#00007F">End</SPAN> <SPAN style="color:#00007F">Sub</SPAN></FONT>
Once that is in place, you can close the VBE. To answer your questions:
1. Is there a way to undo the whole activity? Just in case I screw up, I must know how to get out of it and restore status quo.
There is currently no way to do this. When you run code, it deletes the undo stack. If you want a surefire way to do this, you must code it so, which would be kind of a pain. We can look into this if you'd like.
2. Will this feature work on every spreadsheet I work on(old and new)?
If you put it in your PERSONAL.XLS file, yes (as directed above).
3. I work on lots of spreadsheets with macros built on them (I didn't write those). Will this code ever cause any "conflicts" with those macros?
No, this does not act on any other macros. The only way that would happen is if you had a cell change event, in which case we could add some lines of code to inhibit that.
4. Is this the same code that firefytr mentioned?
I think so.