Althou i have never tried it myself you may be able to accomplish this by placing the content pane of your skin inside of a div with css overflow with attribute auto or scroll and a fixed height. Theres some information about overflow properties here: http://www.w3schools.com/css/pr_pos_overflow.asp

In theory i think it may work. is worth a shot.

off the top of my head I believe you would have something like this as your code:

<div style="height: 200px; width: 250px; overflow: scroll;">
   <table>
   <tr>
   <td id="ContentPane" runat="server" valign="top"></TD>
   </tr>
   </table>
</div>

..its worth a go, cant garentee it thou sinse ive never actually tried.

Good luck and let me know if it works!

Regards,

DrNuke