I\'ll start by saying that my experience with Excel and VBA is limited to what I saw in school. I have programming experience, but in other languages.
I have a file
Worksheet_Change event will do the job if you add a formula into cell which will never be overwritten. Let's say your data are pasted into A1 cell and occupied 5 columns. So, enter below formula into 6. column and row 1.
=COUNTBLANK(A1:A1048576)
Now, you're able to handle/detect paste event ;)