Creating Monthly Data Table From Weekly Data Table

I have a table of data which represents data in different categories by week.

My ultimate goal is to have another table representing the data for each month - for instance - for each of the categories the data for :

06/04/2009
13/04/2009
20/04/2009
27/04/2009

is summed to make the data for the month of April.

The way I'm doing this at the moment is very long-winded

I'm using a whole new table - the size of the original weekly one - for each month. A calculation decides whether to effectively leave a cell blank or insert the appropriate data based on a date being within a particular range.

So in each "month table" there is the same list of week values:

06/04/2009
13/04/2009
20/04/2009
27/04/2009
04/05/2009
11/05/2009
etc.

but for each "month table" only the cells adjacent to the dates within the relevant month will return actual numerical values within them

This is an example of the forumula I am using in these tables:
=IF(AND(($AD7>=MIN($AE$5,$AE$6)),$AD7<=MAX($AE$5,$AE$6)),$C7,"NA()")

Then a master table sums the totals for each month.

I want to be able to keep this table but get rid of the ones for every month as the sheet is getting unwieldy!

I have tried several times to attach the sheet for clarity but each time upon trying to "Submit New Thread " I am getting page not found errors - the sheet is only 133KB and I have tried zipping and sending also - I can't make it any smaller.