Got a spreadsheet that's consecutively numbered.
Need it to keep consecutively numbering as I add and/or delete rows

Example:

1 Blah-blah-blah
2 Blah-blah-blah
3 Blah-blah-blah
4 Blah-blah-blah
5 Blah-blah-blah

If I delete row 3, I need the numbering to continue consecutively -- as it
stands now, if I delete row 3, it will renumber "1, 2, 4, 5..."

Same thing if I add a row -- I need consecutive numbering to appear in the
new blank row (this sounds stupid/impossible even to me and I'm SO NOT an
Excel head)

Help!