Is there an easy way to "exclude" an outlier datum from calculatio

[Luxtron Lenny]

Hi. I regularly analyze large data sets. The data is typically gathered
from experiments and, usually due to experimental mistakes, sometimes we get
an outlier datum. I want to "exclude" or "mask" this point to keep it from
being included in all the follow on calculations (such as means, standard
deviation, and other follow on calcutions). Since this one datum can
propogate to many points depending upon the data analysis, it is usually very
combersume to remove this single point at every stage. Ideally I could just
turn this datum "off" and the calculations would skip this point. I know
this can be done in other programs. Is this possible in Excel?

Thanks,
Luxtron Lenny