Number rows based on content on another column

Hi,

I'm trying to get this code to work, but can't figure out what's wrong with it. I'm trying to number rows on column A (starting on A2), based on how many rows have content on column B. I tried the codes below using both Excel 2010 & 2016, but nothing happens. No error message, no numbers entered.

What am I missing? Is there a better option rather than using Autofill?

Thanks for any help!

Sub Other_Fill()

    Range("A2").AutoFill Destination:=Range("A2:A" & Range("B" & Rows.Count).End(xlUp).Row)

End Sub

Sub Other()

    Selection.AutoFill Destination:=Range("A2:A" & Range("B" & Rows.Count).End(xlUp).Row)

End Sub