Does MarketXLS provide an Excel function that returns historical adjusted close prices for stocks and ETFs, and is a Barchart data subscription required to use those functions?

Yes, MarketXLS provides the historical adjusted close prices. You have to use the “Custom Dates” button on the menu bar. It allows you to filter through different dates, ascending/descending order, and different time frames like daily, weekly, or monthly. This does not require a Barchart subscription unless you need stock data from CME, COMEX, CBOT, ICE Canada, etc. The “Custom Dates” function and other historical data functions should work with all MarketXLS subscriptions. The only historical data that you do not get in the Pro plan is “Intraday historical data”.