Query with variables

I am using the syntax below in the query generator as part of a larger query.  It works fine, however, when the user prompt appears, both customer and vendors show up in the selection list.

/* SELECT FROM [WSB_LIVE].[dbo].[OCRD] T30 */ DECLARE @BPName AS nvarchar(20) /* WHERE */ SET @BPName = /* T30.CardName */ '[%0]'

I would like to limit the selection to customers only, so I modified the query above to the following but it did not change the selection list.

/* SELECT FROM [WSB_LIVE].[dbo].[OCRD] T30 */ DECLARE @BPName AS nvarchar(20) /* WHERE T30.CardType = 'C' */ SET @BPName = /* T30.CardName */ '[%0]'

Any suggestions?