Excel Macro doing mass Input via GreenScreen

I am still digging for exact details, but I received a call this afternoon
from a concerned IT Manager. He has heard of some users using Excel and
Macro's to do larger numbers of data entries via standard greenscreen
sessions. I assume they are populating a spreadsheet from an external
source and then running the macro to run the greescreen input. Anyone seen
this before? Can you stop it by
A. Tasering the user(s)
B. Using a Group Policy to block ALL Macro Use within Excel ( this seems a
little extreme)
C. ??

I am not looking for better or different ways to do this, looking to stop
this method.

Thanks