Summarizing partial data based on date range

Is there a way that I can build a function that will look at only a certain date range, even though my spreadsheet may have more data available? I am trying to compare, day by day, how the departments revenue for 2012 compares to what it was in 2011. I have a spreadsheet that has the 2011 data populated, but since all of 2012 hasn't happened yet, I only want it to compare to the beginning of the month through yesterday. Currently, I am doing it by manually changing my sum ranges each day - it would be nice if I could change one field and it automatically recalculate.