This can be rather complex but I'll try to sum it up as best as I can
and as I'm understanding.

It sounds like you want to "highlight" cells as you hold the mouse
down and go over.  If so I would have a mousedownevent in the cell(s)
you wish to start at that sets a boolean to true that says something
like:  bHighlighting = true;

Then in the mouseover event of the cell(s) I would have:
<td onmouseover="CellMouseOver(this);"></td>
function CellMouseOver(o)
{
if (bHighlighting)
{
  ChangeBackgroundorAttribute(o);
}
}

Now if you need to do it via column/rows, in the past I have used the
value of the cell to have a column or row in there so that I could
determine which row I was working with.  You could use some kind of
naming convention or there might be a way to go up in the row object
to find out what the column/row is.