Hi Zuberi,
I understood exactly what you mean.
Yeah, it's a timing thing....
Meanwhile, with Force Hold, there's no chance to reveal the enchantment after he has declared his move until the move is completed. At which point, it is too late to prevent. Now, you could reveal it after he activates the creature and before he declares a move. That would work.
If he is like most players, he probably declares his intention while he is flipping the action marker, or possibly even before. If so, you should feel justified in interrupting him and saying that you are revealing during the time between activation and movement. The rules require him to activate first, to declare which creature will be acting before actually acting with it. You are supposed to be able to respond to this and if he is trying to deny you that right, you should remind him that you have it.
However, there is a big issue here. Once, I was playing with someone and he moved his mage announcing a move/attack. So, I interrupted him and did exactly what you said. But, he replayed saying that
"I already said that I would like to move and attack, you are interrupting my action... and even worse, you already know that I want to move/attack and you are revealing Force Hold only because of this...". As you can see, it generated a big argumentation.
Last night it was a discussion about Armor Ward. Last week, something else. Even something similar to this (
http://forum.arcanewonders.com/index.php?topic=13987.0) happened to me.
In other words, MW is a fantastic game. But, among my group it is the game that generates more discussions around the rules. We play many other games (Game of Thrones, Magic the Gathering, Netrunner...) and MW is by far the one we waist hours discussing about rules. This is annoying and a huge drawback when compared to the other games.
In my humble opinion, MW could be more consistent. For instance, if with Armor Ward a player can see a possible outcome prior to revealing a enchantment; then Force Hold, Divine Intervention (and all the other enchantments) should behave the same.
I hope you get what I mean and really which to see less rules issues when playing MW.
Cheers,