Two Gateways - Routing Question

Interfaces:
ether1 - 203.114.137.71/28
ether2 - 192.168.100.2/24
ether3 - 203.114.162.41/29
ether3 - 10.0.0.100/8

Gateways:
192.168.100.1/24
203.114.137.65/28

How do I set this MT box so that all my 10.0.0.100/8 clients use the 192.168.100.1/24 gateway and all my 203.114.162.42-203.114.162.46 clients use the 203.114.162.41/28 gateway?

Cheers for your help!

mark routing by source address and add two gateways with routing marks:

Mangle:
http://www.mikrotik.com/testdocs/ros/2.9/ip/mangle.php

Wiki sample about routing mark usage:
http://wiki.mikrotik.com/wiki/Load_Balancing_Persistent