I have two spreadsheets with data based on monthwise

Say Months in a row1 and data in row 2. As shown below:

Jan-10 Feb-10 Mar-10
10 11 12

I am using =HLOOKUP(TODAY(),D11:O12,2,1) to fetch data from sheet 2 to sheet 1 based on current month

What I need is how to fetch data based on previous month.. I have tried
=HLOOKUP(MONTH(TODAY())-1,D11:O12,2,1) but no joy...

Appreciate if someone help me on this....