I have found multiple posts on how to edit the apex:page line so that when the VF page is activated, it saves itself to an excel file:
<apex:page cache="true" contentType="application/vnd.ms-excel#test.xls" controller="StoreController" language="english">
But what I need to do is display the VF page with the panelGrid. Then the user can click a button or link that will export the grid to excel.
I was thinking of just creating a second visualforce page that contains the above apex:page line, but I don't know how to add that logic to a button/link.