Use SUMIF()...
=SUMIF(date-range, date, sum-range)
date can either be hard coded or put into its own cell (preferred) and then referenced.
If you want to sum between 2 dates, change to sumifS()...
=sumifs(sum-range, date-range, ">="&start-date, date-range, "<="& end date()
again, the start date and end date are better referenced, than hard coded[/QUOTE]
Perhaps my 2nd suggestion will work for you, as long as your dates are real dates (try Jonmo1's test)
If it is just text dates (month names), then SUMIF with July should work