Hi Blaire,
If I understand you correctly, then the original workbook
is still intact under it's old name. Since when you use Save As
you create a new workbook. Unless you never saved the
file before. Excel is a spreadsheet application, but the word
spreadsheet is rather ambiguous in Excel, as to whether
one would be referring to a workbook or a worksheet.
If you opened the file and altered it, then used 'Save as' and renamed it,
you should still have the original file, completely unchanged, in it's
original
location.