How can I scroll a div field using javascript?

Hello experts, I have a web page with a large amount of information in a div field.  This page will be displayed on a small touch screen hand held and the default scroll buttons that come when you assign the property of overflow to a div tag are too small.  I am trying to use two buttons one to scroll up and the other to scroll down.  I have only been successful in scrolling to the top, I thought by substracting or adding to the scroll height would allow me to scroll using buttons.  Any ideas?


I know this still needs work, i will need to keep track of the current position.
function scroll_up()
{
  var div = document.getElementById('div-fork');
  h = div.scrollHeight;
  div.scrollTop = h-10;
}

function scroll_down()
{
  var div = document.getElementById('div-fork');
  h = div.scrollHeight;
  div.scrollTop = h+10;
}

<a onclick ="scroll_up();"><IMG alt="" src="images\arrowup.gif"></a><BR>
                                                      <BR>&nbsp;
                                                      <a onclick="scroll_down();"><IMG alt="" src="images\arrowdown.gif"></a></td>