its exactly what u want:
http://cband.linux.pl/
Name CBandLimit
Description Specifies bandwidth limit for virtualhost
Context <Virtualhost>
Syntax CBandLimit limit
limit - bandwidth quota size, available units: K (kilo), M (mega), G (giga), Ki (kibi), Mi (mebi), Gi (gibi)
Example CBandLimit 10M
Specifies 10 * 1000 * 1000 bytes bandwidth quota
CBandLimit 10Mi
Specifies 10 * 1024 * 1024 bytes bandwidth quota
Name CBandExceededURL
Description Specifies a URL where mod_cband should redirect all requests to a virtualhost when the configured transfer limit is exceeded NOTE: If you don't specify the exceeded URL location then standard 503 Service Unavailable will be sent
Context <Virtualhost>
Syntax CBandExceededURL URL
Name CBandPeriod
Description Specifies a period after which a virtualhost's usages are cleared
Context <Virtualhost>
Syntax CBandPeriod period
period - available units: S (seconds), M (minutes), H (hours), D (days), W (weeks)
Example CBandPeriod 1W
CBandPeriod 14D
CBandPeriod 60M
just do some reading mang