We need to extract the unique values from a range and have them copied to
another range. However, we are looking for a solution that will
transparently keep the unique destination range values updated as the source
range values change. Is this possible?

Is there some formula or array formula that will extract the unique values
from another range and keep them updated as they change? If not, is there a
simple macro that could perform the job and be automatically triggered by
cell edits to the source range?

Our goal is to extract the unique account numbers from a large list of
transactions and then summarize the transaction subtotals for any given
account number. We are open to any ideas, thank you.