Here's how I ballpark it:
(1) Look at the package's nutrition information. Sugars should be on there: figure out how much that is in grams.
(2) Go back to your original recipe calculation, and add that much simple sugar to your recipe. (fructose, corn sugar, dextrose, sucrose. . . they're not the same, in terms of ABV, but we're looking for a ball-park number here, so don't stress too much about what you choose.)
(3) The program should spit out the new OG and, once you get a measured FG, you can figure out your ABV.
Primary 1: Hasty IPA
Secondary: Soured Golden
Kegged: American Wheat
Bottled: Belgian Golden Ale.
Planning: American Amber