Answer: Generally, rapid to moderate growth rate trees and shrubs will reach 5-6 feet tall in 7-9 years, while moderate to slow growth rate trees and shrubs will take 9-11 years to reach the same height. Soils, weather, weed and grass competition, and animal/human damage will effect growth rates.
Boxwoods are generally considered to be moderate to fast growers, but unless you begin with rather large shrubs, they won't reach 7' in only 2-3 years; it typically takes a full year for the roots to become established before shrubs and trees will begin to grow well. If it's immediate height you're interested in, you may want to plant 10-gallon plants.
Here at the Q & A forum we give gardening advice but we do not have information about the stock your nurseries might carry. I can only suggest you contact the larger nurseries in your area and request a special order. Most will be happy to assist you.
Best wishes with your new landscape!
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