For example:

Germany:
A BOH - GAL
A SIL S A BOH - GAL
Russia:
A RUM - GAL
A UKR S A RUM - GAL

Then even if the Austrian army in Galacia moves out, neither the Germans or the Russians will be able to get in.

On a slightly unrelated point, if something attacks Bohemia (or if something attacks Ukraine, but not both at the same time) and the army in Galacia holds (or bounces in, say, Budapest) then it would be dislodged in the typical 2 on 1 (specifically, 2 on 1 on 1).

When a unit is attacked, it cannot perform a support move or support hold, unless the support move is against the attacking unit, and the attackee unit is not dislodged. Whether or not the attackee has support holds is irrelevant.

I'm not sure that's what he's asking.. he may need to clarify his question..
Ja, in the first scenario, are 2 units separately attacking a third unit, which has a unit supporting it to hold, or do you mean that a unit attacks with another unit ordered to support its move to a third unit which has a unit supporting its hold?
Similar questions about the second scenario.. Do you mean that 2 units are separately attacking a unit, each with a unit supporting its move, or do you mean that a unit attacks with a unit supporting its move against a unit that has 2 units supporting its hold?
There may be an easy answer to his question...
You cannot tell units to support to hold a unit that was given orders to move. You can only support to hold a unit that was given a hold, support, or convoy order; just like you can only support a move of a unit that was given an order to move. So, if you have 2 units told to support a hold on a unit that was given an order to move, those 2 units just wasted thier orders.
Does this help?

@Ukla: Yes, we do have it wrong. I understand the first part now; it's asking what happens when a unit which has one support is attacked by one unit with one support. What the next part of the question means, I don't know.

Could someone clarify?

I think he is confusing supporting holds and moves. He says if one unit is supporting another to hold can that other do an offensive move. Well it can but the support to hold is then invalid and the unit would be dislodged

For example, A supports B move to C. D supports C to hold. If C tries to move then D's support of C to hold is invalid and doesn't happen. So then it is A and B against C and C is dislodged and B moves in.

What you can do is if your opponent has A support B to C and on your side you have D support E to C then you can have C move. B and E will bounce because both are supported by one unit. If C successfully moves then the country is left open. If it doesn't then it just sits there with ducking its head in its foxhole while the battle rages on around.

Its called the Beleagured Garrison rule. Basically if all attacking forces bounce then the occupying unit is unaffected (except for the cut support).

well, this is what i get for dashing off a quick forum query on the way to work before i've had my coffee. :-)

You are right in that i made an error in my original assumption. I had momentarily confused a moving unit (which cannot be supported) with a supporting unit (which can be supported). I was remembering a case from a previous game in which the attacked unit's support for a third attack was cut by its being attacked and applying it to a case in a present game where i was worried that the attacked unit was going to move. It was a panic post quickly written before i'd completely thought out the situation and before my brains had been jump-started by coffee and nicotine.

:-)