Try:

=COUNTIF(CX:CX,"B*")

=COUNTIF(CX:CX,"O*")

"Bob" wrote:

Column CX contains entries that either begin with a "B" or "O". I need to
count the number of cells whose contents begin with "B", and count the number
of cells whose contents begin with "O".
I wrote the following formula, and even saved it as an array formula, but I
keep getting a circular reference error:

=COUNTIF(CX:CX,LEFT(CX:CX,1)="B")

Any help would be greatly appreciated. Thanks.
Bob