How can I "fake" the appearance of merged cells (like in Excel)

[Roger Eller]

I have a table field with about 10 columns. Some of the cells may contain
the same data as the cell above and/or below it.  I want to visually
portray these occurances as a single cell with the text centered within the
visually larger cell.

How would you approach this problem?  Would you overlay an opaque field
whose rectangle is that of the combined cells?

I need it to scroll too.  Thoughts?  Creative solutions?  No, not gonna use
Excel.  ;-)

~Roger