[Skunkworks] PK Alias

Hi, My database table looks like this *TransactionID* *TransactionNo * *Register* 1 23/2009 Probate 2 23/2009 Administration 3 25/2009 Finance 4 26/2009 Strategy TransactionID is the primary key and is autogenerated. A register can only hold a unique TransactionNo though different registers can share the same TransactionNo. Is there a way that I can make TransactionNo field to be unique, and is there a way of coming up with a Primary Key Alias to represent the unique TransactionNo for each Register? Regards. Ouya Obunga