CustomExtensions.cs

using UnityEngine;
using System.Collections;

public static class CustomExtensions
{

    public static void EditKeyframeValue(this AnimationCurve animationCurve, int key, float value)
    {

        Keyframe[] keys = animationCurve.keys;

        keys[key].value = value;

        animationCurve.keys = keys;

    }

    public static void EditKeyframeValue(this CandyCoded.Vector3AnimationCurve animationCurve, int key, Vector3 vector)
    {

        animationCurve.x.EditKeyframeValue(key, vector.x);
        animationCurve.y.EditKeyframeValue(key, vector.y);
        animationCurve.z.EditKeyframeValue(key, vector.z);

    }

}