Connect to Excel then format within a cell



I need to format text in cell in an Excel work*** and I need to do this using C#.

I've seen code that will set the format for the whole cell, but I just need to format one character in that cell.

Example:
The cell has this text in it: H20

I need to use C# to change the "2" to be a subscript.

A similar question was asked before, but I don't think the reply answered the part about only formatting part of the text in the cell:

( the link will probably wrap )
http://groups.google.com/group/microsoft.public.dotnet.languages.csharp/browse_frm/thread/feaee4eccb1364e4/d6501f0007c0b0f3

TIA for any help on this.
-BEP
.