Instructions:

To use this simulator, first click on the unit type for attacker and defender.
The terrain type is defaulted to "Plains" and the unit number are defaulted to "10", but you can change them to anything you want.
Next up, at the bottom, click the level of bonus to apply (for attacks from multiple sides).
Finally, click "BATTLE!" and the outcome probabilities will be calculated and displayed at the bottom.
After the battle is done, you can click "Set" (by the results) to set the respective most probable outcome as the current unit number.
Rinse and Repeat!

Using the Bonus Calculator
Determining your attack bonus can be tricky - this calculator takes out the guess work.
First, click on any of the hexes to mark where the first attack occurred - it will be marked as "1st."
Then click on the hex where the second attack occurred - it will be marked as "2nd."
The resulting bonus effect will then show up under "Total Bonus."
Continue clicking the hexes for as many attacks as you have. Also, click on the DFA to add the distant attack bonus.
If you make a mistake, click on "Back" to go back a step, or click on "Reset" to erase everything.
Finally you can click on "Set" to set the calculated bonus as your current battle bonus.

Email me with comments or feedback.