I don't know if a realy understod your question but maybe this can help you.
When you double click in the table row you copy the last character to clipboard.
Here is the code that I made:
// You can use any function to copy here
function copyToClipboard(textToCopy) {
var input = document.createElement("input");
document.body.appendChild(input);
input.value = textToCopy;
input.select();
document.execCommand("Copy");
input.remove();
}
function copyLastColumn(tr) {
copyToClipboard(tr.lastElementChild.innerHTML);
alert('copied to clipboard');
}
<table border="1">
<tr ondblclick="copyLastColumn(this)">
<td>a</td>
<td>b</td>
<td>c</td>
</tr>
<tr ondblclick="copyLastColumn(this)">
<td>d</td>
<td>e</td>
<td>f</td>
</tr>
<tr ondblclick="copyLastColumn(this)">
<td>g</td>
<td>h</td>
<td>i</td>
</tr>
</table>