Number Field That Adjusts Based on Gaps and Duplicates?

Hello everybody; this is a great forum. Here's my problem: My database tracks keys and keyrings given to staff. Each record has a field called "KeyRingOrder" which is simply a sequencial number that denotes where that key is on the key ring. The problem is that if our locksmith takes key # 2 off of a maintainence key ring (~20 keys), then the user has to manually change the KeyRingOrder of keys 2-20 to keys 3-19 (and visa versa if he adds a new key).

Does anyone know the code to have Access automatically detect a gap or a duplicate in the KeyRingOrder field and adjust it accordingly? The keyrings are viewed individually in a query, so the KeyRingOrder is technically a primary key within the query. However, there is a separate KeyID field that the database actually uses as the primary key for the database.