Adding Additional 'and' Information Into SQL Statement In Excecute SQL Task

I am using an execute SQL Task item on the control flow to be used as input for the foreach loop container. I have a select statement but, based on other information provided before this is executed, additional 'and' information may need to be added onto the SQL Statement before execution. For example, the select statement may read:

select applicatonid, created, createdby
from application
where referred by = 'xxx'

But based on information obtained from an ini file, something like:

and referred date = '2008/05/28'

may need to be appended to the SQL statement. I have tried setting the SQL statement as:

select applicatonid, created, createdby
from application
where referred by = 'xxx'

+ @addlwhere

and defined the @addlwhere in the parameter mapping but it raises an error. Has anyone run across this type of need and how did you resolve it? Thanks!