Yes, you can borrow. Just remember that Use Year and Calendar Year are different. It may help to make yourself a chart for planning purposes. You don't indicate your Use Year, so this is just an example.
April Use Year -- April 2004 Points are good for trips from April 1, 2004 through March 31, 2005. Also borrowed from April 2005 so those points must be used for trips ending on March 31, 2005.
April 2005 -- Points already moved to 2004
April 2006 -- Points are good for trips from April 1, 2006-March 31, 2007. Can also be banked forward or borrowed for trips between April 1, 2005-March 31, 2006.
April 2007 -- Points are good for trips from April 1, 2007-March 31, 2008. Can be banked forward or borrowed for trips from April 1, 2006-March 31, 2007.