А если снаружи
<table style="float: left">
<tr class='sales_confirmation_no' datum="foo">
<td>foo</td>
<td>foo</td>
<td>foo</td>
</tr>
<tr class='sales_confirmation_no' datum="bar">
<td>foo</td>
<td>foo</td>
<td>foo</td>
</tr>
<tr class='sales_confirmation_no' datum="baz">
<td>foo</td>
<td>foo</td>
<td>foo</td>
</tr>
</table>
<input type="checkbox" style="margin-bottom: 10px"><br>
<input type="checkbox" style="margin-bottom: 10px"><br>
<input type="checkbox" style="margin-bottom: 10px"><br>
<script>
trs=[].map.call(document.querySelectorAll("tr"), function(x){return x})
;[].forEach.call(document.querySelectorAll("input[type=checkbox]"), function(x, i){
x.onclick=function(){alert(trs[i].getAttribute("datum"))}
})
</script>