Can Pile-on be used when you are being blocked

[DaImp]

The senario is as follows:

It is player A's turn. Player A blocks player B and rolls a skull. Player A is knocked over. Player B has Pile-on. Can player B use pile on to add his strength to the armour roll against player A? Remember that it is not player B's turn.
The start of the rule reads as follows and here in lies the confusion:
"The player may use this skill after he has made a block... "
Does this mean you can only use Pile-on when you initiate the block - ie in your turn?
I made the ruling that you have to be the player making the block to use pile-on, but I am not 100% sure that this is correct.

Can anyone give me a clear ruling on this?

[TiMuN]

I would say no.

You can only use it when you actually chose to fall over an oponent in your turn.

[Asmodan]

Its just as the rule say, after he (the player with piling on) have made a block.
Not when he is being blocked.