Sure, you can still use it. I'd just figure the "gravity" distance and plug that in as the distance then use the computed MOA drop for that new "gravity" distance.
If you're using Exbal, you must have a computer. I'd assume you have Microsoft Windows. In Windows you have a calculator. Start the calculator, select VIEW from the manu bar and change to Scientific. Make sure the Scientific option includes a checked Degrees radio button. Enter the angle you desire and press COS. The result is the factor you multiply the Line-Of-Sight distance by, the new answer is the "gravity" distance. Enter the final answer into Exbal and you have the (perhaps if everything else is working) correct answer for the angled distance.
You can make a handy little chart of Cosines if you like and carry it with you.