Auto sum/grouping by row based on month

[witchcraftz]

I have data that auto populates from another sheet, it puts data into rows:

Actual
Planned
Forecast
Earned

I need to auto-sum my data for each row by month. So for example anything in the Actual row, where the date is between 2012/12/01 and 2012/12/31 should be summed together.

Pivot tables don't work since they only work on column arranged data and need to be rebuilt when the data changes.

Any ideas?

Sample sheet attached