I'm creating a list of notes within excel. Due to it's nature, it will be
very long, and also constantly updated with input from others. What I'd like
to do is this:

Setup Column A so that all cells in Column A become a row #, one after the
other, starting at a certain point in my document and continuing onwards.
E.g. Cmn A/Row 5 content = 1
Cmn A/Row 6 content = 2
Cmn A/Row 7 content = 3
etc.. etc...., if I ever add something to the end of the list, it will
automatically add the proper number in Column A.

Can someone help me create and tell me how to setup such a script?

If you could also create it in such a way that it uses variables (e.g. start
numbering from Row XX with starting number YY), that'd be great :D.

Thank you!!