Hi there
It would be easiest using a sql statement. However there would need to be something common for all orders to make this work. Eg you could use the date. The satement based on date would be:
update `zen_orders` set `orders_status` = 3 WHERE zen_orders.date_purchased >= '2007-01-15' and zen_orders.date_purchased <= '2007-01-21'
You would need to change dates as per you range and if you don't use the 'zen_" prefix in your database you would also remove the prefix from above statement.