表格一行内单元格拖动性

小弟要实现一个表格内单元格的能拖动性，希望各位能帮忙啊
表格如下，具体要实现C2,C3，C4一行中：首先保持这一行的总宽度不变，然后能通过鼠标拖动来改变三个单元格所占比例，希望大拿能帮忙，在线等回复啊
<table border="1" style="height: 60px">
                                        <tr>
                                            <td align="center" colspan=6 bgcolor="gray">
                                                C1</td>
                                        </tr>
                                        <tr>
                                            <td align="center" colspan=2 bgcolor="gray">
                                                C2</td>
                                            <td align="center" colspan=2 bgcolor="gray">
                                                C3</td>
                                            <td align="center" colspan=2 bgcolor="gray">
                                                C4</td>
                                        </tr>
                                        <tr>
                                            <td align="center" colspan=3 bgcolor="gray">
                                            C5</td>                                  
                                            <td align="center" colspan=3 bgcolor="gray">
                                                C6</td>
                                        </tr>
                                        <tr>
                                            <td align="center" colspan=6 bgcolor="gray">
                                                C7</td>
                                        </tr>
                                    </table>