Editing parts of layers using mute tool

This seems like it should be simple, but the process is not working for me, using X1.  I punched in a new part of a vocal and wound up with both the old punched part and the new part playing back.  I am trying to replace the old part of the original layer with the new part in the second layer.  I have tried the Mute tool, but it only seems to work if placed at the bottom of the whole track, not at the bottom of the upper layer, which is the part I want to mute.  So it only lets me mute the part I want to keep.
 
So how can I play back the track with the original punched-in part muted and replaced with the newly recorded part (it is only one measure)?       Thanks.

IIRC The mute tool works like this:
if you want to mute a section of an audio clip click and drag the tool on the lower half of the clip. If you decide to un-mute click and drag on the top half of the clip.

duplicate
 
 

Thanks for responses.  Regarding how to use the must tool, I think I understand but have not been able to make it work.  I wonder if that could be because I am working with V-Vocal clips?
 
Some things I don't understand:
1.  Why do I have 2 waveforms on each of my layers.  Is that just an indication of stereo?
2.  Why can't I play two layers at once?  If I Solo one layer, it will automatically Mute the other one.  I need a way to solo both at the same time.
The fact that I have 2 waveforms for each layer, means that I have a section above and below each waveform, a total of 4 sections.  If I mute by scrolling in the lowest section, it seem I have difficulty un-muting it because if I scroll in the upper layer, it does not relate to the lower waveform which is where I muted.
 
By the way, I did get my song finished but I had to use separate tracks rather than separate layers.  But I will follow through on some of the suggestions, such as checking out the instructional video.
 
I have not installed X2 yet.  Does all this become easier with Take Lanes?
 
But does anybody have a clue as to how I was messing up using the layers?   Thanks.