Create and Pass custom date to form, query and report

I have created a db for a non-profit, contacts, volunteers, donors,
etc.

Our statistical year ends on the last Sunday of September and starts
on the first Monday following.

Our statistical month ends on the last Sunday of a given month and
starts on the first Monday following the last Sunday of the previous
month.

My users are not computer savy and need as many default options as
possible.

I have a table with two fields ID 1-12 (nbr) and Month January -
December (txt) with corresponding query. On my SB I have a combo box
based on this query that defaults to the current month using the
default =Format(Date(),"mmmm"). The user will be able to select a
previous month.

I need help in taking the results of the cbo to two text boxes, one to
show beg of stat month and one to show end of stat month (ex: Feb 2004
dates were 1/26/2004 - 2/29/2004). Dates will then be used as default
for entering volunteer detail records, and reporting volunteer hours
by stat month. I am looking for advice on how to make the
calculations.

Thanks LizM