Can you voluntarily suppress the effect of a continuous magic item you are wearing?

I would like to ask my DM if it is possible to craft a Continuous Cloud of Knives (Player’s Handbook II) Ring, but it could be a little awkward in certain situations, a swarm of knives orbiting around you is unlikely to help in social interactions. Is it possible to voluntarily suppress the effect of the spell?

Should I just opt for the Use-Activated item?

Cloud of Knives


Level: Cleric 2, Sorcerer 2, Wizard 2,

Components: V, S, M,

Casting Time: 1 standard action

Range: Personal Target: You

Duration: 1 round/level

You conjure a cloud of sharp knives around you. The knives float in the air around your upper body, pointing in the direction you look.

Each round as a free action at the beginning of your turn, you can release one of these knives at any target within 30 feet that you can see. This is a ranged attack that uses an attack bonus equal to your caster level + your key ability modifier. Each successful hit deals 1d6 points of damage +1 per three caster levels (maximum +5) and threatens a critical hit on a roll of 19-20. Damage reduction applies to knife attacks from this spell. The knives are treated as magic for the purpose of overcoming damage reduction. Material Component: A knife.

Optional Material Component: Using a silvered dagger (22 gp) in the casting of this spell allows the knives to overcome damage reduction as if they were both magic and silver, but the knives deal 1 less point of damage.