I'm trying to alter this table column
RECREATE TABLE PBM_CLAIM (..., MULTSRCCDE CHAR(1) NOT NULL COLLATE
ISO8859_1);

To this domain
CREATE DOMAIN D_MULTISRC AS CHAR(1) CHECK (VALUE IN ('M','O','N','Y'))
COLLATE ISO8859_1;

With this command
ALTER TABLE PBM_CLAIM ALTER COLUMN MULTSRCCDE TYPE D_MULTISRC

And I get this error

ISC ERROR CODE:335544351
ISC ERROR MESSAGE:
unsuccessful metadata update
cannot delete
COLUMN RDB$2133
there are 6 dependencies

I can't find any dependencies, and I don't know where to go from here.
Any ideas?

Thanks, Rick DeBay