Sand Whirlwind from Taldor Echos of Glory

[Martin Sheaffer]

Quick question about the spell sand whirlwind:

A whirling cloud of sand strikes the target, blinding it and
hampering its ability to speak. To speak while affected by the
spell, the target must make a Concentration check (DC equal
to the DC of this spell). If the target tries to cast a spell, the
Concentration DC increases by the level of the spell being cast.
A successful Will save negates the blindness but not the speech hampering
effect.

The question is does this spell force an automatic concentration check any time the victim tries to cast a spell or just when something else would force a concentration check?

a) Victim tries to cast a spell and due to the sand must make a concentration check at 15 + 2*spell level + spell level due to spell.

b) Victim tries to cast a spell and due to being adjacent to a enemy decides to cast defensibly so must make a concentration check at 15 + 2*spell level + spell level due to spell.

c) Something else :)

[Paul Watson]

If the spell has verbal components, the target must make a concentration check to speak. The DC is equal to the DC of Sand Whirlwind+ the spell level of the spell being cast.

Otherwise the normal concentration checks apply.

At least that's my reading of it.

[Devilkiller]

Would a caster using Silent Spell need to make a Concentration check if casting while under the effects of this spell? I felt that the Concentration check should only apply to spells with verbal components, but the player who used the spell was convinced that the whirlwind distracts the target and forces Concentration checks on all spells, even those without verbal components.

Either way this seems like a strong anti-caster spell since many casters don't have Silent Spell and Combat Casting might not apply to these particular Concentration checks. The Will save only negates the blindness, and there's no SR, so the Concentration checks seem tough to avoid.