Good Morning All!!

I am working on a spreadsheet that I would like to have data in one column added and the answer to populate in another column, but the I would like the data to take into consideration a date range before populating the answer. I think I thoroughly confused the words, but see the example below for claification. Any help is greatly appreciated!!!

Column A Column B Column C Blank Column Qty for Sept Qty for Oct
09/01/2013 Jane Doe 3 4 6
10/01/2013 John Doe 2
09/15/2013 Doe Jane 1
10/15/2013 Doe John 4

In the table above, I would like for the column labeled "Qty for Sept" to look at column A and for any dates in September, I would like it to add the numbers indicated in Column C and populate the answer under "Qty for Sept". Same for "Qty of Oct", I would like for the answer to be populated based on the dates entered in Column A that are October dates and add the numbers in Column C. I don't want to have to "sort" the spreadsheet to be able to calculate these numbers, I would prefer that it be done automatically with its current set-up. Again, any help would be greatly appreciated!!!

Mandi