=SUM(--(FREQUENCY(IF($C$1:$C$10<>"",MATCH($A$1:$A$10,$A$1:$A$10,0)),ROW(INDI
RECT("1:"&ROWS($A$1:$A$10))))>0))

and

=SUM(--(FREQUENCY(IF($C$1:$C$10="",MATCH($A$1:$A$10,$A$1:$A$10,0)),ROW(INDIR
ECT("1:"&ROWS($A$1:$A$10))))>0))

which arearray formulae, it should be committed with Ctrl-Shift-Enter, not
just Enter.

Note the second will fail if you have blanks in column A

--

HTH

Bob Phillips

(replace xxxx in the email address with gmail if mailing direct)