I would start by downloading one of the Local Government editing map templates like the Water Utility Network Editing and Analysis template. You may not be editing a water utility but that template can really show you how the Attribute Assistant can work. It was actually an add-in created for that template.
What you are describing sounds like the Nearest Feature Attributes method.
The best way to figure it out is download a template like the one mentioned above and play around with the DynamicValue table and see what the results are. Be sure to turn on the log file and check it if things aren't working the way you think they should.
Here are a couple of lines I use in my address point layer:
This line grabs the house number from the HouseNum field of a polygon layer (parcels) named AddressingPointHouseNumbers and puts it in the ADDRNUM field of my SiteAddressPoint layer. The search distance is 5 feet. It's a pretty simple line in the table and saves me a bunch of time.
Hope that helps.
Jeff
Jeff Ward
Summit County, Utah