i want to Load balancing of LAN subnet. please guide. layout is attached with email.

Try this: http://wiki.mikrotik.com/wiki/Manual:PCC
but in my case LAN is not directly connected with Mikrotik. but LAN users are able to reach/ping mikrotik.
You can try some routing tricks, but personally, I would use a load balancer, like and F5, for load balancing servers and things like that on the LAN. There are a wide array of those types of devices. I was recently told that there is an open source and free load balancer as well, but I have never used it.