add extra content into exported excel sheet in asp.net

I am exporting the selected items in gridview to excel. Now the exported excel should contain something like "Excel downloaded on: TODAY_DATE" (where 开发者_JAVA技巧TODAY_DATE is today's date in mm/dd/yyyy format).

My Question: How can i append the text (as mentioned above) in the exported excel?

Thanks!

The same can be done through html.writer("Content Comes here!").

The above solution is valid only if an excel sheet is generated from HTML.