The ItemCommand event will fire for each command so you can distinguish the different export types.
Then, you can try changing the property and format strings directly as per your needs. If this does not help, cancel the command (e.Canceled = true), modify the properties, and call the corresponding MasterTableViwe.ExportToXXXX() method (replace XXXX with the appropriate format, e.g., Pdf, Docx, as per the command name).
If you want this to propagate throughtout the application, you can use ASP_Themes. You can define the handler in a global class and apply the theme to all pages.
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