MonoBehaviour.OnTriggerStay(Collider)

Description

OnTriggerStay is called once per frame for every Collider other that is touching the trigger.

This message is sent to the trigger and the collider that touches the trigger. Notes: Trigger events are only sent if one of the colliders also has a rigidbody attached. Trigger events will be sent to disabled MonoBehaviours, to allow enabling Behaviours in response to collisions.

	// Applies an upwards force to all rigidbodies that enter the trigger.

	function OnTriggerStay (other : Collider) {
		if (other.attachedRigidbody)
			other.attachedRigidbody.AddForce(Vector3.up * 10);
	}

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    void OnTriggerStay(Collider other) {
        if (other.attachedRigidbody)
            other.attachedRigidbody.AddForce(Vector3.up * 10);
        
    }
}

OnTriggerStay can be a co-routine, simply use the yield statement in the function.