用javascript控制iframe滚动的代码

现在有一个横向的IFRAME,需要通过点击iframe外的一个图片来横向滚动iframe内的一个html页,但又不想让看见iframe的滚动条,请问如何解决啊？？？？

<img   src="demo.gif"   onmousedown="window.timer=setInterval（"a.document.body.scrollTop++",10）"   onmouseup="clearInterval（window.timer）">
  <img   src="demo.gif"   onmousedown="window.timer=setInterval（"a.document.body.scrollTop--",10）"   onmouseup="clearInterval（window.timer）">
  <iframe   name=a   src="test.html"   scrolling=no></iframe>

demo.htm

  <iframe   name="in"   src="in.htm"></iframe>
  <div   align="center"   style="height:130px;width:243px;">
      <script>var   timer;</script>
      <br>
      <input   type="button"   value="up"
  onmousedown="timer1=setInterval（"parent.frames["in"].scrollBy（0,-1）",10）"
  onmouseup="clearInterval（timer1）">
      <input   type="button"   value="down"
  onmousedown="timer1=setInterval（"parent.frames["in"].scrollBy（0,1）",10）"
  onmouseup="clearInterval（timer1）"   >
  </div>


  in.htm

  <br>0<br>0<br>0<br>0<br>0<br>0<br>0<br>0<br>0<br>0<br>0<br>0<br>0<br>0<br>0<br>0<

横向滚动..

  demox.htm

  <iframe   name="in"   src="inx.htm"></iframe>
  <div   align="center"   style="height:130px;width:243px;">
      <script>var   timer;</script>
      <br>
      <input   type="button"   value="Left"
  onmousedown="timer1=setInterval（"parent.frames["in"].scrollBy（-1,0）",10）"
  onmouseup="clearInterval（timer1）">
      <input   type="button"   value="Right"
  onmousedown="timer1=setInterval（"parent.frames["in"].scrollBy（1,0）",10）"
  onmouseup="clearInterval（timer1）"   >
  </div>


  inx.htm

  <body   scroll=no>