Do a search for Linked lists and double linked lists.

You may be able to do something like this.

Add two fields to your DB. These fields hold the Primary ID of the records on either side of the current record.

DB Feilds

(RECORDID ;INFO ;NEXT ;PREVIOUS) (5 ;anything ;6 ;4) (6 ;anything ;7 ;5) (7 ;anything ;8 ;6) (8 ;anything ;9 ;7)

Now if you need to move record 5 between 7 and 8 the only records you need to alter are the Next and Previous fields of record 4,5,6,7,8 or if you want to move 5 between 500 and 501 you will only have to change 4,5,6,500,501. You can then index and sort based on the Next and Previous fields. Just my 2 cents