CFCONTENT has nothing to do with generating excel sheets.You're just defining that output data is sent in binary form, with a certain mime type. Creating an Excel sheet is something completely separated. If you use already a third party component for this, check if it supports multiple worksheets.
A csv file is not an Excel worksheet (conceptually) at all. There are no features like sheets. It's dummy data with just commas, quotes, values and linefeeds.
One alternative would be to create an Excel XML worksheet. I haven't tried thismyself, but here are some pointers:
CF9 is of course the easiest solution with its cfspreadsheet tag, if you can upgrade.
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