DSum function

[Irene]

i have a query which i have three field that is defect_type, date and qty. i
want to calculate the percentage of the type of defect. but i cant get the
overall total which is group by month. i have try using DSum function. my
formula is like this %Reject[qty]/DSum([qty],"q_daily_reject"))*100 . but
it was take the total of the qty. i want it group by month. i want the total
of the month not overall of the qty. how i can do it? i know need to set the
criteria, but i dont know how to set it. can anybody help me?

Thanks!