Domain Restriction MaxClients in .htaccess

[Mandi]

I am willing to restric the MaxClients for a specific domain, let's say 10 simultaneous visitors.
I tried creating a .htaccess with the directive
MaxClients 10
but it gives Internal Server Error, Any other way to restrict this number for a domain or a specific subdomain!?

 

[Mandi]

in the error logs there is:

.htaccess: MaxClients not allowed here