Help needed in scripting

hello
i am using the expense tracker app from the zoho market place
http://creator.zoho.com/talshani/expense-tracker-tal/share/edit/
i would like to upgrade, i have looked in scripting faq and have not found what i was looking for.
i would like to :
1. create several sum cell who will count my spendings by the category i have
spent and will make it equal to zero each month.
2. have a scheduled email for those sums
thanks
tal