If you touch anything or anyone while holding a charge, even unintentionally, the spell discharges... Alternatively, you may make a normal unarmed attack (or an attack with a natural weapon) while holding a charge... If the attack hits, you deal normal damage for your unarmed attack or natural weapon and the spell discharges
For as long as the spell lasts, any touch range spell of 4th level or lower that you cast can be delivered by the spectral hand. The spell gives you a +2 bonus on your melee touch attack roll, and attacking with the hand counts normally as an attack.
So it is incorporeal ("having no physical body" though technically any detached hand has no physical body - tongue in cheek), which means it cannot actually touch anything except other incorporeal creatures, intentionally or otherwise. That definitely seems to mean it can go through the ceiling without triggering. Wall of Force "blocks ethereal" ... technically I think incorporeal is not blocked, but spells are explicitely blocked from passing through the wall, so that still forces the hand to go around.
The spell text explicitely allows you to deliver spells anyway, either via normal touch or via attack, so the fact that it cannot touch the target is not relevant. The hand has no listed speed, so there is no penalty to casting a spell on the hand then moving it around the wall.
Conclusion: OK, I'm convinced. As long as you can maintain line-of-sight on the hand as it goes carefully over the top of the wall of force, you can use it to cast past the wall.
