If I understand you right, you are in the same situation as me.
I bought in Feb of 2000. I have a December use year. Our original points are 1999 points. I also sold back 75 points.
What I did was have my initial purchase as Dec 1999. I then put in a trip called Magical Beginnings and made it cost 75 points. This leaves you with 75 1999 points and then Dec 2000 you have another 150 points.
I hope it helps.