MonoBehaviour.InvokeRepeating

function InvokeRepeating (methodName : String, time : float, repeatRate : float) : void

Description

Invokes the method methodName in time seconds.

After the first invocation repeats calling that function every repeatRate seconds.

JavaScript
    // Starting in 2 seconds.
// a projectile will be launched every 0.3 seconds
var projectile : Rigidbody;
InvokeRepeating("LaunchProjectile", 2, 0.3);
function LaunchProjectile () {
var instance : Rigidbody = Instantiate(projectile);
instance.velocity = Random.insideUnitSphere * 5;
}