What about @@CPU_BUSY and @@IO_BUSY
if you checked those two values e.g. every 10 seconds and the @CPU_BUSY had increased 8 seconds I would assume that it was running on 80%, that without the VBA and the security issues it imposes.
Sys.dm_os_ring_buffer gives CPU usage % directly. Refer http://strictlysql.blogspot.com/2010/06/finding-cpu-utilization-in-sql-server.html
Regards,
Raj