the value for the list should use the event ID column. make sure the select list form is set to use the post method, and it should have a submit button
make note of the select list name.
on the details page, create a recordset to return the requested event. in the recordset filtering section, set the filtering to use the EventID column Equal to Form value, and enter the name of the select list.
you may find the database starter kit tutorial helpful: