请教如何实现下面这 一个功能

Question

http://www.javaeye.com/upload/attachment/40404/5eb36f49-4cbf-3b09-8ac7-65a6be0330f7-thumb.jpg?1222421811

Answer 1

   比如选中11111， 然后点“》》” 111，就会去右边， 
如果在右边先中111， 然后点 “《《”111就会去左边，
这种功能怎么实现 ， 有没有类似的网站或系统可以参考一下的呢        _____________________
date1   |____________________|        ______________________
date2   |_____________________|________
|button|
--------——————_        ---------
|11111     |         |  5555   |
|2222      |         |         |
|333333    |         |        |
|          |     》》|        |
|          |    《《 |        |
|          |         |        |
|          |         |        |
|          |         |        |
|          |         |        |