How can i add a menu item to the standard button 'Export'

Hi All,

I have a requirement, For an ALV data export i need to provide two options for the customer.

one is 'Export to Excel' and another is 'Export to CSV'. As we know Export to Excel is a standard functionality provided as menu button, i have created another button to perform Export to CSV and it works well. But customer doesnt want this as a separate button and asking to add this as another menu item to the standard button 'Export' .

How can i achieve this?

Thanks,

Ramakrishna