In ISBoxer make 3 new keymaps.

MOVEMENT-ALL
MOVEMENT-RANGE
MOVEMENT-MELEE

WASD / UpDownLeftRight for you not keymapped.
WASD / UpDownLeftRight with ALT for Melee
WASD / UpDownLeftRight with SHIFT for Ranged
WASD / UpDownLeftRight with CTRL for ALL

Then make two ATGs for Ranged and Melee. Add characters respectively.

Now in the keypress actions direct the keypress actions to the ATGs they should be sending the commands to.

That's how I do it.