Need previous year's "YTD" sales to automtically update to change in current month

My 2013 YTD sales automatically compute because i just have it as SUM of the range monthly sales are entered into. However i want to compare 2013 YTD to 2012 YTD. I need 2012 value to automatically compute based on which MONTH it is. i.e. it is now June, so i need 2012 YTD of Jan - May (2012).

This is how my excel is setup:
D12-O12 have months labelled out "January" ---> "December"
from D15 - O15 have my monthly sales from 2012.
C14,C15, C16 have the dates 2011, 2012, 2013 accordingly.
in cell B5 i have =today() which looks like (Jun-13)
i also have exactly one year ago to the date in cell B6 "=EDATE(B6,-12)"

I want the 2012 YTD to automatically add the additional months sales from 2012 in accordance with the automatic month change in cell B5 OR B6.

I've fiddled around with various SUMPRODUCT, SUMIF, SUMIFS, OFFSETS and not having any luck. The problem is this is an approved format so i cant change the layout. That is why i need help.

Probably it can be done with an pivot table.

If you want that solution the data need to be set up like a table. (data in rows (instead of columns))

Hi and welcome to the forum

I would suggest you upload a sample work book, (all sensitive data removed), showing what data you are working with, a few examples of what your expected outcome is, and how you arrived at that
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click "select files" find your file, click "open" click "upload" click 'done" bottom right. click "submit reply"

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Assuming you will always have a value in the month, try his, copied down...
=SUMIF(D13:O13,">0",D12:O12)

OK, but your other tenants have paid, so that month will not be zero. And if some have not yet paid, you will have nothing to include from them anyway?

So how would you propose to handle that?

paid...supplied info...pretty much the same thing

If 1 client has given the info, say up to May, and the rest up to June, then that 1 will be calc'd to May, and the rest will be cal'd to June

Add an extra month's data (or remove 1) from sheet2 and see what happens on sheet1

Or are you saying that if we are in June, you want them a;; to sum to June, whether they have info in June or not?

paid...supplied info...pretty much the same thing

If 1 client has given the info, say up to May, and the rest up to June, then that 1 will be calc'd to May, and the rest will be cal'd to June

Add an extra month's data (or remove 1) from sheet2 and see what happens on sheet1

Or are you saying that if we are in June, you want them a;; to sum to June, whether they have info in June or not?

I have been playing around with your file a bit and added a few things to streamline it a bit. Take a look and see what you think? I have added a formula that will add up 6 months of data for all entries, even if some have only 5 (or 4) months of data.

Thanks so much, both of these options are great and will run them by everyone.