Peter,
Are you using DIAdem's Excel Import Wizard? By "Excel file" do you mean a tab- or comma-delimited ASCII file that Excel can read in easily, or do you mean a file with the extension "*.xls"? You certainly could not search through an *.xls file to find CR/LF characters.
If you use the ASCII or Excel Import Wizard to create an *.STP file for the "Excel" file in question, then after the *.STP file is loaded you have access to a whole range of variables, starting with Ascii... or Excel... which completely outline the structure of the ASCII or Excel file, including things like the row in which the channel comments are, etc.
Why don't you send over your Excel file and I'll be able to help you a lot better.
Regards,
Brad Turpin
NI