JS实现鼠标单击单元格时 单元格里的Check为选中

Table ： MyGrid1

function MyGrid1.onclick(e)
{
if(!e) e = window.event;
var obj
if(window.event)
obj = e.srcElement
else
obj = e.target

if(obj.tagName == "TD")
{
if(obj.children[0] != null)
{
if(obj.children[0].checked == true)
{
if(obj.children[0].disabled == false)
obj.children[0].checked =false;
}
else if(obj.children[0].disabled == false)
obj.children[0].checked =true;
}
}
}

<table id='MyGrid1' cellspacing='0' cellpadding='0' border='1' borderColor='#000000' >
<tr height=18><td><INPUT class='i0' name='Rq:_0' type='text' value='2009-08-24' readOnly></td><td>2009-08-24</td><td>星期一</td><td><input name='breakfast:_0' type='checkbox' style="width:27px; height:27px"/></td><td><input name='lunch:_0' type='checkbox' style="width:27px; height:27px"/></td><td><input name='supper:_0' type='checkbox' style="width:27px; height:27px"/></td></tr>
<tr height=18><td><INPUT class='i0' name='Rq:_1' type='text' value='2009-08-25' readOnly></td><td>2009-08-25</td><td>星期二</td><td><input name='breakfast:_1' type='checkbox' style="width:27px; height:27px"/></td><td><input name='lunch:_1' type='checkbox' style="width:27px; height:27px"/></td><td><input name='supper:_1' type='checkbox' style="width:27px; height:27px"/></td></tr>
<tr height=18><td><INPUT class='i0' name='Rq:_2' type='text' value='2009-08-26' readOnly></td><td>2009-08-26</td><td>星期三</td><td><input name='breakfast:_2' type='checkbox' style="width:27px; height:27px"/></td><td><input name='lunch:_2' type='checkbox' style="width:27px; height:27px"/></td><td><input name='supper:_2' type='checkbox' style="width:27px; height:27px"/></td></tr>
<tr height=18><td><INPUT class='i0' name='Rq:_3' type='text' value='2009-08-27' readOnly></td><td>2009-08-27</td><td>星期四</td><td><input name='breakfast:_3' type='checkbox' style="width:27px; height:27px"/></td><td><input name='lunch:_3' type='checkbox' style="width:27px; height:27px"/></td><td><input name='supper:_3' type='checkbox' style="width:27px; height:27px"/></td></tr>
<tr height=18><td><INPUT class='i0' name='Rq:_4' type='text' value='2009-08-28' readOnly></td><td>2009-08-28</td><td>星期五</td><td><input name='breakfast:_4' type='checkbox' style="width:27px; height:27px"/></td><td><input name='lunch:_4' type='checkbox' style="width:27px; height:27px"/></td><td><input name='supper:_4' type='checkbox' style="width:27px; height:27px"/></td></tr>
<tr height=18><td><INPUT class='i0' name='Rq:_5' type='text' value='2009-08-29' readOnly></td><td>2009-08-29</td><td>星期六</td><td><input name='breakfast:_5' type='checkbox' style="width:27px; height:27px"/></td><td><input name='lunch:_5' type='checkbox' style="width:27px; height:27px"/></td><td><input name='supper:_5' type='checkbox' style="width:27px; height:27px"/></td></tr>
<tr height=18><td><INPUT class='i0' name='Rq:_6' type='text' value='2009-08-30' readOnly></td><td>2009-08-30</td><td>星期日</td><td><input name='breakfast:_6' type='checkbox' style="width:27px; height:27px"/></td><td><input name='lunch:_6' type='checkbox' style="width:27px; height:27px"/></td><td><input name='supper:_6' type='checkbox' style="width:27px; height:27px"/></td></tr></table>