I'm relatively new to Mikrotik management and networking itself.I have a Mikrotik CCR1009. Is there a way I can set a internet access time limit for exp 08:00 to 17:00 for my employees using mac and/or ip filtering of the pcs ?Or anything I can set up in Firewall or NAT? If not I have all user connected via LAN to a Cisco CATALYST 3750G Switch. Is there anything I can configure there regarding this matter? Thanks in advance

Because you treat your employees like kids...try kid control ;-)
First part was a little joke, kid control will do this just fine.

I'm a network employee myself.That's what my boss requested. First you ask,then you answer. Thanks either way