Hi,
On your grid view you may have pop up menu say "Paste". Once you copy from excel the content is available in the clipboard. Then right click and select paste which will actually read the clipboard data, format it and populate the grid view.
you may refer to this article
Clipboard handling with .NET[
^] which explains how to handle clipboard data.
Format the clipboard string may be a bit hard as the strings may not have a data separator, but yet it is possible.
Export to csv and import option will be easy for coding, same time more work for the user.