I keep getting "There is no primary or candidate keys in the referenced table 'customer' that match the referencing column list in the forwign key 'fk_co_zip'"

BO1:  Customer - cu_number (PK), cu_name, cu_zip_number

BO2:  Zipcodes - zip_number (PK), zip_text

I'm trying to make a foreign key between cu_zip and zip_number.

I'm running on MS SQL 2005 Express Edition.

Hope that some of you can come up with the gold answer (i'm sure it is stragiht forward and simple)

Best regards

Ulrik Müller