I currently have 30 months of data from Apr 2006 to Dec 2007 arranged in
columns B to V.

I want to have a line graph which shows Jan to Dec and compares two years,
that is, last year would be Apr 06 to Mar 07 as 1 line and current year would
be Apr 07 to Dec 2007. When I add Jan 2008, the line will automatically add
the new month of data.

I want to use my current data without manipulating the data into 1 column
for Apr06 to Mar 07 and so on. Is this possible?