Can't Create A Foreign Key Using Non_primary Key Fields

Howdy all !
I'm just a bit on the frustrated side cause I want to create a foreign key but SQL Server won't let me. :(

I have table A with a primary key of main_id
I have table B with a primary key of another_id

Table A has a corresponding field called another_id.

I'm trying to create a foreign key between Table A & Table B on another_id but since it's not the Primary Key in Table A I get the following error:

There are no primary or candidate keys in the referenced table 'A' that match the referencing column list in the foreign key 'fk_classB_classA'.

Am I missing something totally obvious here? Why should I have to create a foreign key on a primary key?

What I find interesting is that I can create the relationship from enterprise manager but when I script it out is when I run into problems.

Here's the script I'm using:

Begin Code

alter table B add
constraint fk_classB_classA foreign key
(classB) references A (classB)
on delete no action
on update no action

End Code

Any help is greatly appreciated.

tam