joint regions problem...

I have two vertical row ranges, and want to combine them in a formula. The old range was "data", the new is a combination of two ("Feb_11", "Jun_11") - the two regions are all rows, and contiguous, and a subset of the old "data" region.

It works fine in most formulae, but fails in a count usage; Is this just another Excel anomaly, or am I doing something wrong?

I've tried parenthesizing it in various ways, which should not be required, but still didn't help.

Thanks.

Works:
=AVERAGE(AZ:AZ ) [old]
=COUNTIF(AZ:AZ data, ">="&(AY162*(AZ:AZ Total))) [old]

=AVERAGE(AZ:AZ (Feb_11,Jun_11)) [new]

Fails: (#Value)
=COUNTIF(AZ:AZ (Feb_11,Jun_11), ">="&(AY162*(AZ:AZ Total))) [new]

If I evaluate the two ranges separately, ti works fine.
=COUNTIF(AZ:AZ Feb_11, ">="&(AY162*(AZ:AZ Total)))
+COUNTIF(AZ:AZ Jun_11, ">="&(AY162*(AZ:AZ Total)))

Oddly(?) enough, if I define a new name:
Group1 = Feb_11,Jun_11

Then all the arithmetic formluae work find on it, but still the Count fails in the same way.