[PF] Immediate action Counterspell spell

[Bugbeartrap]

Background: I am a big fan of playing spellcasters in tabletop and of Magic: the Gathering. One aspect of magic that I've never seen used in 3.5 or Pathfinder is the option to counterspell. It's too situational or useless because in 3.P, Offense is the only defense. I'm currently playing a magus styled after the Izzet and wish to add some mechanics to back up the flavor. Counterspelling is an iconic part of the card game, and synergistic to the magus because of their anti-spellcaster sub-theme.

Problem: I'm having trouble deciding what spell level this would fall into. It is based off of dispel magic, so 3rd level is a starting point. However, the spell is stripped of all its utility of removing buffs, suppressing magic items, or dismissing summoned monsters (on top of being useless against spell-like abilities). This would seem to lower the spell a level, but how much does making it an immediate action raise it? I feel like a 3rd level slot is right, but a 4th level slot is too much.

Counterspell
School Abjuration
Level: Magus ?, Sorceror/Wizard ?
Components: V, S
Casting Time: 1 Immediate Action
Range: Medium (100ft + 10ft/level)
Target: One Spellcaster
Duration: Instantaneous
Saving Throw: none
Spell Resistance: no

Counterspell targets a spellcaster and is cast as a counterspell. Unlike a true counterspell, however, Counterspell may not work; you must make a dispel check to counter the other spellcaster's spell. You make one dispel check (1d20 + your caster level) and compare that to the targetted spellcaster's caster level (DC = 11 + the spell's caster level). If you succeed the target's spell is negated with no results.

Edit: This is my first homebrew post, so let me know if I'm missing anything obvious.

[bobthe6th]

Definitely sounds fun... Perhaps the slot is variable? It can counter spells of equal or lower level? So you can counter 1st level spells with the same, or with second level spells.

[Silvanshei]

I really like this spell as I have always thought normal counterspelling to be mostly useless. I would say this is a 4th level spell as it does the same thing as dispel magic, except it is an immediate action. What, if any, would be the limit to the bonus on the check from caster level?

[failbarian21]

Making the spell 4th level does seem to be a little much, since if you're using it on a magus, you wont get it until 10th level, and even then you begin with only 1 of that level. If you are to keep it at 3rd level, my suggestion is perhaps fiddling with the bonus the opponent gets. Perhaps raising the opponents base DC bonus by 2 points? This makes a very strong spell a little harder to pull off, while letting you get the spell that much earlier.

[Bugbeartrap]

Thank you for the feedback, everyone!

I really like this spell as I have always thought normal counterspelling to be mostly useless. I would say this is a 4th level spell as it does the same thing as dispel magic, except it is an immediate action. What, if any, would be the limit to the bonus on the check from caster level?

In pathfinder, dispel magic has no caster level cap, so I would like to keep the mechanics the same. I would also like to point out this does only the least versatile (and least used) part of that spell.

@Failbarian: Instead of changing the DC of the check, the check could be made at a penalty. This would keep the mechanics consistent, as Greater Dispel Magic has a +4 caster level bonus.

EDIT: It's possible this could be made into different levels for magus and sorc/wiz (ex: magus 3, sorc/wiz 4)