Since you post here, I assume your AutoCAD runs some VBA code that automates Excel to read some data from the sheet, or write some data to the sheet.
So, it is very likely that the error you showed is due to the VBA code in AutoCAD, not something wrong with the *.xls file.
Therefore, you need to examine the AutoCAD VBA project (*.dvb, which is loaded into AutoCAD at some point when AutoCAD runs), if you know a bit AutoCAD VB, or you have to send the *.dvb file for some to look into, should the VBA code is not password-protected.