Advanced Table/CSS issues

I'm trying to set up a page (on IE 5.5+ only) where I've got a table to display (table-layout=fixed), and each <TD> element actually contains a <SPAN contentEditable style='overflow:hidden'>Text goes here</SPAN>

I have three questions:
1. How do I specify the line height for each table row to be 1, so that I won't get any overflow onto the second line, but so I don't have to choose pixels?

2. What I'd REALLY like is when there is an empty cell or cells to the right of a cell that has overflow, for that overflow to spill to the right and show (more of) its additional text. This is what happens in an Excel spreadsheet.
At the same time, if someone clicks on one of those empty cells, they should be able to edit it. (Are Z-orders the way to go here?)

3. Can I conveniently identify which cells are overflowing?

Thanks for any tips you may have,

Csaba Gabor from New York

Sample table:
<TABLE border=1 style='table-layout:fixed;width:3in'>
<TR><TD style='border:groove 1px'>
<span style='height:22px;overflow:hidden' contentEditable>This is a very incredibly long cell that doesn't know what to do with itself
</span></TD>
<TD>Cell 2 of Row 2</TD>
</TR></TABLE>