Dynamically get an associated field?

This is a slightly convoluted scenario.  I'll do my best to describe the situation.  I have two tables with related but not identical data.  The project number is the key in the Projects table and the activity number is the key in the Activity table.  Additionally, the Activity table is a child table of the Projects table.  There is a location number in the Activities table that is associated with the activity number and there can be multiple location numbers at the same address because at one point the location number was associated with a particular device rather than the physical address.

What is the best way to dynamically associate the location number to each related project number.  One additional complication, it is possible (in fact probable) to have multiple activity numbers for each project number, although the location number ideally will be the same .

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Paul Peterson
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