Finding related records within date proximity

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Hi all. I have an event file with each event occurring on some date. I have another file, of activities, each with its date. The events and activities can be related via a common denominator, bookstore ID. What I need is to identify those activity records that fall within 1 week before and two weeks after any event to which they are related. Many of the activity records are not related to any event records and will be omitted. But some activity records could be related to more than one event record. I doubt that this is Find question but thought I would start here. I would appreciate any ideas for approaching this problem.