As tamu91 has said, it all depends on your use year. If your use year is in the first half of the year, then your July 2006 trip falls in your 2006 use year. You could bank your '05 points into 2006 and borrow your '07 points and have 150 points to use for your July '06 trip.
If your use year is in the second half of the year then your July 2006 trip falls in your 2005 use year and you could use unbanked 2005 points and borrowed 2006 points giving you 100 points for your July 2006 trip. You would not be able to use your 2007 points in this case.