using stdevp across multiple fields in one record

[damien]

I am trying to get a calculated field in a query which
will calculate the standard deviation (population) across
a number of fields in the one record. Some of the fields
will have null values.
When I try to use the STDEVP worksheet function on more
than one field, I get an error message that I am using the
wrong number of arguments.

but when I exchange the stdevp function for the averagea
function it works.

any help would be great.