Summarising information

[Daniel Tinker]

I have a subform (based on a query, in datasheet view) on
my main form, which may contain several rows of data. I
need to summarise one of these fields, to appear as an
answer on the main form ie. if the answer to the question
for all the rows of data is YES, then the summary should
be YES. If the answer to the question for any one of the
rows of data is NO, then the summary should say NO. So
far i have only been able to summarise the first row of
data using the expression IIf.

I would be grateful for any help.

Daniel