Muting and Starting of Clips

So I want to use Sonar for live performances meaning that I loop 4 bars and press record and record tracks as I need to add different things to the song. Thus, I'm continuously muting different tracks throughout the song since the song changes. However, I also unmute things when they come back and I was wondering if there is a way that when I mute or unmute, the track only does it at the end of that bar instead of immediately so I don't have to worry about accurate timing.
 
Here's an example of what I want to do: 
 
Any help with ways to mute easily would be appreciated.
 
Also, I'm having issues with recording new tracks at the beginning of the loop. If I'm even a millisecond too early before it loops, it starts the note at the end of the loop and then it doesn't carry it over to the beginning. Is there a way to make it carry over a note played at the end of the loop to the beginning?
 
I know this is probably confusing but if you watch the example video, it should give you a good idea of what I'm trying to do.
 
Thanks in advance for any help.