Hi,
As our friends explained there seems to be definite issues when you using the excel 2013 with the dashboard and there are lot of discussion has been happened with bitter experience in the community.
Few are listed below.
In future it can rectified by the SAP Team, meanwhile please educate the customer about the difficulties in using the ms-office and ask to downgrade it, rather than running behind the problem.
Hope this helps!!!
--SumanT