Place this in httpd.conf:
SetEnvIf Request_URI "winnt\/system32\/cmd.exe" dontlog
SetEnvIf Request_URI "winnt\/system32\/cmd32.exe" dontlog
SetEnvIf Request_URI "winnt\/system32" dontlog
SetEnvIf Request_URI "scripts\.\.\%" dontlog
SetEnvIf Request_URI "scripts\/" dontlog
#
CustomLog...