I'm tring to set up a correlation matrix where a table contains the
same headings in both the x and y axis. I then use this formula to
find the correlation:

=CORREL($B$2:$B$253,B$2:B$253)

This returns 1 since it is the correlation of itself. The next column
over produces this formula:

=CORREL($B$2:$B$253,C$2:C$253)

What is the best way to write a formula that does not require me to
manually switch the B to a C for each and every row --- over 300 of
them.

=CORREL($C$2:$C$253,C$2:C$253)

Thanks for any help you can offer.