bind variable

I have a visual basic application that uses a sql query that uses bind variables to extract a result. I have noticed that i can't use bind variables in a from clause. Is there anyway to pull the max of one column and then another column in the table that corrsponds to that row? Here is my sql query.

 "select ec.ec_export_number,ec_date from event_campaign ec, " &_

        " (select max(ec_export_number) as maxexport from event_campaign" & _

        " where EC_PURPOSE = :event_purpose AND EC_ITEM_SENT
= :item_sent" & _

        " and EC_SQL = :sql_totalcount ) maxresults where " & _
        "  ec.ec_export_number = maxresults.maxexport and EC_PURPOSE


= :aevent_purpose AND EC_ITEM_SENT = :aitem_sent " & _

        "  and  EC_SQL = :asql_totalcount"