Is there any way to get a Incremental autonumber when I have a database replicated. I want to use the Master for design changes only so I should'nt have any problems with duplicate Numbers.

Access doesn't know that and it doesn't give you the option of using incremental autonumbers. You will probably have to go with the roll your own varity. Use a two field primary key. The first field should indicate the replica number or something that uniquely identifies a copy of the db. The second field is a sequence number that you generate yourself. If you don't know how to do this, find one of the many posts that will tell you. Look for autonumber and DMax().