How to create a Google Spreadsheet of tweets with the same hashtag:

Very soon after the event, use the FREE website: Search Hash

external image searchhash.png
and follow these easy directions!

Download hashtagged tweets as a spreadsheet to archive or analyse

n.b. Twitter only makes the last few days' tweets available to search, and limits search results to around 1,500 tweets." Super thanks to Joyce Valenza for finding this great work around!