Done !! Thanks a lot.
But i have change limit.
lpMMI->ptMinTrackSize.x = 1000;
lpMMI->ptMinTrackSize.y = 700;
in place of
lpMMI->ptMaxTrackSize.x = 1000;
lpMMI->ptMaxTrackSize.y = 700;
I have done this change because i do want to stop user from resizing from maximum to minimum. not from minimum to maximum.