Invoicing by selection

I am doing volunteer work for the local Chamber of Commerce. Their database is in Access 2010 and has a main member info form with a subform for payments (membership and/or services).
I want to be able to select (highlight) a payment entry and generate an invoice for just that (or those, if more than one are selected) payment.
I am thinking an action button that calls the query, but am unclear how to code it for just those payments. Also, the subform is in datasheet view, so I am unsure how to embed the button in the datasheet.