Vrrp???

RouterOS General
1

can i change the vrrp mac address

2

http://wiki.mikrotik.com/wiki/Manual:Interface/VRRP#Virtual_MAC_address

Virtual MAC address
VRRP automatically assigns MAC address to VRRP interface based on standard MAC prefix for VRRP packets and VRID number. First five octets are 00:00:5E:00:01 and last octet is configured VRID. For example, Virtual Routers VRID is 49, then virtual MAC address will be 00:00:5E:00:01:31.
Virtual mac address can not be manually set or edited.

That is exactly as the RFC dictates.
http://www.faqs.org/rfcs/rfc3768.html, section 7.3