Microsoft Outlook is the program designed for this task — it’s not just an e-mail software, it’s for planning and tracking meetings and places the meetings on the invitee’s calendars. You can easily see who has accepted or declined the meeting invitation and you can set it up to remind people 30 minutes (or whatever) prior to the meeting. It’s great. You really ought to try this. I think it will save you a lot of time and frustration.