Research the command line interface node and the Excel command line options.
Use the command line interface node to launch Excel with the intended file on pressing the button.
This is just one more simple option.
Hi,
Alternatively you can try the VI described here:
https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019YKHSA2&l=en-US
This will actually open any document with its default application.
Attached is a small example.
Regards,
Raphaël.