Ctrl +C (copy) and Ctrl +X (cut) are Windows shortcut keys rather than Excel
specific and I don't think its possible to disable them in Excel. I'm not
even sure that it's possible to do it in Windows - there may be a registry
tweak, but I don't know it.

What you could do is write a macro that does nothing (or something
neglibible - say, display a message that the key combination is not
available) and assign the macro to the Ctrl +C and Ctrl +X combinations. This
will not, however, prevent copying and cutting from the menus, toolbars or
context menus.

You can read about this at:  
http://msdn2.microsoft.com/en-us/library/aa195807(office.11).aspx

You could use
With Application
   .OnKey "^c", "" 'Copy shortcut disabled
   .OnKey "^v", "" 'Paste shortcut disabled
End With

This basically sets these keys to nothing ("")

To enable them again, you would use
With Application
   .OnKey "^c" 'Copy shortcut enabled
   .OnKey "^v" 'Paste shortcut enabled
End With

Without the "" at the end, it returns them to their original state