Bukkit

Negation of potion effects.

If possible I am looking to negate certain potion effects. For example:
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I have a region set up stating that upon entry give the player blindness 2 indefinitely.

If they have a white dyed helmet that gives them Blindness 0 and enter the region then blindness 2 does not effect them being that the blindness 0 overrides the regions flag.
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Is this something that will be possible?