Passing database name to stored procedure

Hi everyone,

Please tell me, how to send database name to the stored procedure.

For instance (doesn't work):

CREATE PROCEDURE "SelectPurchaseOrder" (IN DbName VARCHAR) LANGUAGE SQLSCRIPT AS

BEGIN

  SELECT * FROM :DbName.OPOR;

END;

SET SCHEMA is not a case, I need to modify data in two databases in a single query.

Regards, Evgeny.