declare @dbname varchar(50)
select @dbname=dbname from base..corpdb where id=...
exec('select '+@dbname+'.dbo.fn_name(paras) as colname')
--or:
--exec('select '+@dbname+'.dbo.fn_name(paras) as colname from ...')
--or:
--exec('select ... from '+@dbname+'.dbo.fn_name(paras)')