Q 92:

Quote Originally Posted by Spell Compendium
Slapping Hand (Evocation [Force])

Level: Sorcerer 2, Wizard 2,
Components: V, S, AF
Casting Time: 1 standard action
Range: Medium (100 ft. + 10 ft./level)
Effect: One Tiny hand
Duration: Instantaneous
Saving Throw: None; see text
Spell Resistance: Yes

You complete the spell and blow into the leather glove. Immediately a blue-white, translucent hand appears next to the enemy and smacks it across the side of the head—not enough to hurt it, but hard enough to give others nearby a chance to attack.

This spell distracts the subject, causing it to immediately provoke attacks of opportunity from creatures threatening its space. The spell allows no saving throw, but a slapped creature can negate the effect with a DC 20 Concentration check.

Focus: A leather glove.
If this spell is timed to strike a spellcaster while trying to cast a spell (with a ready action), must the target makes two separate Concentration checks with different DC (one to avoid attack of opportunities, one to not flub the spell)? Or would the second check (to not flub the spell) only be required if the first is failed?