selecting cells

I am working in VBA and am trying to select ranges.

This statement works to select all the rows that are used
in columns A to C

Set rng = Range("A1:C" & Cells(Rows.Count, "C").End
(xlUp).Row)
rng.Select

I am trying to select all the rows from 3 on down in
columns N and O. This does not work. What am I missing?

Set rng = Range("N3:O" & Cells(Rows.Count, "O").End
(xlUp).Row)
rng.Select

Where can I get a listing of the VBA syntax that I can use
for programming? This hunt and peck way of learning is
for the birds.