Meetings

I have a recurring meeting on Monday and Thursdays.  When I set up the meeting, I didn't know what I was doing and set it up for 7 days a week as I couldn't figure out how to do it for Monday and Thursdays.  I would like to edit this to the proper days, but need the meeting numbers to remain the same as they are listed in a national registry so people anywhere can join the meeting.  Any ideas on how to go back and re-edit this?