Thank you Don,

Sumproduct must be one the greatest functions of Excel.
Your solution is perfect.

Chip: My application is a Lims system for a water analysis laboratory.
Samples can have an "a" or "b"' code which implies they are still
incomplete.

Thanks,

Michael
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"Don Guillett" wrote:

Try this idea. Need NOT be array entered.
=-SUMPRODUCT((ChecksC={"a","b","c","d"})*(ChecksD))