Monthly Average in a PivotTable

[Pflugs]

I have a Workbook of my personal expenses including dates, amounts, and
categories for budgeting purposes. I want to create a PivotTable that
summarizes the data by month and by type. I also want it to display a year
to date total and an average across all months in the years so far.

I created a table that had the types in row area and the dates in the column
area. I grouped the Dates by month and got the look I was going for.
However, I can't get it to show the average I described above. How do I tell
the Table to take the Grand Total of Amount over the Months and divide it by
the number of Months?

Thanks,
Pflugs