presumably this is an Access problem?
don't rely on the autonumber value being anything other than making a row unique. if the number must have significance outside the system then you probably have to roll your own numbering system.
you don't know what interval there will be (most db's are one but that doesn't hold).
there is nothing in the SQL spec that says an autonumber system MUST start at one in intervals of one its merely a quick method of ensuring that the each row has a unique piece of data.
in a multi user system its possible to have rows hit the table and secure an autonumber value in a random sequence, there is no guarantee that the number will be allocated in the order you'd expect. say you had several people entering data at the smae time, the autonumber sequence int he Access world is normally allocated at the time the record is first saved not first edited / created.
it possible that numbers may be missing (ferisntnace if the user creates a record but ultimately decides not to save it or if a record is deleted. so if your system requires a contiguous set of numbers then you MUST roll your own solution or be a lot cleverer in the way you use Access. by cleverer that means putting in some VBA behind the forms to cater for this juncture and handle accordingly something you cannot do if you sue the datasheet view and enter data directly into the tables
I'd rather be riding on the Tiger 800 or the Norton