Complex VLookup and then adding drop down functionality

Hello,
Please see attached sheet below .

Bascially I would like to do a Vlook up first, pulling out YTD (year to date) values and monthly values for year 2011 and 2012 respectively.

Then I will like to insert a drop down box in the specified area that will give me 2011 JAN TD, 2011 FEB YTD etc , then 2012 JAN YTD, 2012 FEB YTD etc

and monthly figures 2011 JAN, 2011 FEB etc , then 2012 JAN, 2012 FEB

I hope I am clear here

Thanks in advance for your valuable time and effort