Newbie Question--Can you coordinate multiple armies attacking a single province?

[DragonRider]

As an additional note, if you hit "y" while targeting a province, it will open up the army setup screen for all the units moving INTO that province next turn, making it easier to set up their formation so they fit together.

Though this makes me wonder...if my armies in A and B move to converge on C, but an enemy army in C simultaneously tries to march against A...is there a chance that A and C will have to fight without support from B? The rules when two provinces try to attack each other at the same time get kind of tricky.