Copy and paste error (blocks changes!)

[X11start]

I made a stupid mistake and now I would like to find a way to avoid it: I copied a portion of a drawing (using CTRL+C) and pasted it into another (CTRL+V). The problem is that the copied part contained blocks that were already present with the same name in the new drawing. However, the blocks in the new drawing were slightly different.
Is it possible to create a lisp or something that warns: 'Attention: the drawing already contains blocks named XXXX'?

[GLAVCVS]

Perhaps someone knows a better way.
In my opinion, this could be done with reactors.
That is, in your AutoCAD session, there should be two latent reactors: one that activates after "copyclip" is executed and looks for the most recent DWG in the "temp" folder and saves its name in a global variable; and another that activates just before "pasteclip" is executed (:vlr-commandWillStart) and tracks the blocks of the DWG where the "copyclip" was created and the blocks of the current drawing.
There may already be a Lisp published in this forum that does this job, and some veteran can help you locate it.

[Nikon]

3 hours ago, X11start said:

Is it possible to create a lisp or something that warns: 'Attention: the drawing already contains blocks named XXXX'?

Good question. Such situations are common. It would be good, along with the warning, 
to add index 1 to the names of the inserted blocks, for example.

[X11start]

Thank you very much, I also thought that the solution was to use Reactors... but creating a Lisp of this kind is way beyond my abilities! I hope that someone among the 'gurus' of this forum can help me. Thank you.