To rename "MyNewSheet" to just before "OldSheetNow" of the workbook "D:\XLSFiles\C.XLS" the following syntax would be used:
ConvertXLS.EXE /S"D:\XLSFiles\C.XLS" /T"D:\XLSFiles\C.XLS" /P106 /1"MyNewSheet" /2"OldSheetNow"
Note: You don't have to specify Boolean (TRUE/FALSE) parameters that are FALSE. Nor do you have to specify parameters that are empty.
The /S and /T switches specify input and output workbook respectively, which in this case is the same workbook. You can optionally keep the input file unchanged by specifying a different name or path for the output file.