Agent's query:

$StartDate.month==7 & $StartDate.year== 2011

See Date.month and Date.year.

Of course, the above only works for July 2011. To change the target month or year, you could fiddle with the query but a less techie way might be to add two Number-type user attributes, $MyMonth and $MyYear. Set these these as key attributes for your agent. Now use the query:

$StartDate.month==$MyMonth(agent) & $StartDate.year== $MyYear(agent)

Now, to reset the month/year of enquiry, you open the agent and change $MyMonth and/or $MyYear.

BTW, one other question.  Can an agent like this return a result to the UI, e.g. "number of items returned in query."  If so, how would you write the express? How would it show up?

Perfect, thanks!