It could be that the workbook was created in another version of Excel. Excel will alway re-calc a workbook that is not the current version. Try saving the file locally to see if the problem disappears. Otherwise, there are three easy ActiveX solutions you can implement:
1. Set the File Open option Read-only to True
2. Set the Close Workbook option SaveChanges to False
3. Set the Workbook property Saved to True before closing