How to disable a "cut" section from being copied to clipboard

I am having trouble with Audition's copy/paste/clipboard system. I use Audition to edit audio for audiobooks, and one of the things I have to do is copy and paste room tone over noisy or unwanted sections. The process looks like this (this is all done in Waveform Editor on .wav files): 1) I copy my room tone track (which is one second long), 2) select the unwanted portion in the audiobook track, 3) cut the selected portion, 4) and paste from my clipboard. The problem is that when I select and cut the unwanted portion, Audition copies that selection to my clipboard (!) and I end up pasting what I just deleted. My temporary solution has been to switch to the room tone track and copy the room tone after every time I select and cut the unwanted portions, but this is taking way too many clicks. Is there any way to disable this feature? Is there a workaround/shortcut that I can setup to cut down on my clicks?

I have tried setting up a Paste Mix shortcut, but the problem with this is it does not paste exactly one second of room tone. I need exactly one second of room tone to be pasted, but "Paste Mix" simply overlays/overwrites however many seconds selected with that many seconds of room tone. For example, 1) I select three seconds of unwanted audio to replace it with one second of room tone, 2) I "Paste Mix" the selected portion with room tone, 3) resulting in not one but three seconds of room tone.

Basically, can I setup my copy/paste/clipboard to work like it does in a word processor (e.g. if after copying "Goodbye" I select and backspace "Hello", "Hello" is not copied to my clipboard)? Can I "lock" my clipboard?