Calculate Average Weekly Income For Business?

I have created a table for a business to monitor all income and expenses within a financial year of that business. This table contains raw data for example, date, income/expense, wholesale amount, retail amount etc. So when the business makes a sale for example I enter in the date of the sale, type of sale, wholesale and retail amounts etc, and i do this for every sale I make.

What i need to do is figure out a way to calculate the average monthly and weekly income to date so as the financial year continues and i make more sales i will continue to enter more data into this table and it will automatically adjust to the new weekly or monthly average income. This way i always have an actual and live average for every cent the business has made as the year progresses and i can use this to budget for the business. I would also like to know what the income is for the current week or month. that way i can say for example on average the business makes $4000 a week and in this week it has made say $5000.