logs of exporting excel

Does anybody know how/where to add logs to record what a man is exporting to excel ? 

or which file shall be modified to add the log trace.

for security reasons, we need to record the information of exporting data to excels.

regards,

Fred.yy.Lin
Delta Networks, Inc.
186 Ruey Kuang Road, Neihu, 
Taipei 11491, Taiwan
Tel: +886-2-8797-2088  ext.3443




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