Steps to reproduce:

1. Attach Calendar.xls to a Confluence page
2. Insert > Other Macros > Office Excel > Specify the file name as Calendar.xls > Specify the worksheet name as ThisWeek > Click Preview or insert the macro to the page
3. The result is Error rendering macro 'viewxls' : com.benryan.conversion.ConversionException: java.lang.NumberFormatException: For input string: "3-2$C":
   

NOTE: The same issue is not reproducible in Confluence 3.4.9