Use a subquery to filter on the foreign key values from the other table. For example, the BBCM_CONSTITUENT table is set as the Target table but can reference the BBCM_CONSTITUENTCODES table using the following expression:

[BBCM_Constituent].[ConstituentID] IN (SELECT [BBCM_ConstituentCodes].[ConstituentID] FROM [BBCM_CONSTITUENTCODES] WHERE [BBCM_ConstituentCodes].[ConstitCodeDesc] = 'TEST')