gistfile1.cs

using UnityEngine;
using System.Collections;

public class UpDownAnimation : MonoBehaviour {
	public float endtime;
	public float topposition;
	//x or y or z
	public string direction;
	// Use this for initialization
	void Start () {
		AnimationClip clip = new AnimationClip();
		AnimationCurve curve = AnimationCurve.Linear(0f,0f,endtime,0f);
		Keyframe key = new Keyframe(endtime/2,topposition);
		curve.AddKey(key);
		clip.SetCurve("",typeof(Transform),"localPosition."+direction,curve);
		clip.wrapMode = WrapMode.Loop;
		animation.AddClip(clip,"clip1");
		animation.Play("clip1");
	}
	
	// Update is called once per frame
	void Update () {
	
	}
}