Manish
for the same karantaka express book a ticket from bangalore to gulburga ( kK has a seprate quoto for gulburga and to northbound)
from gulburga to kopargaon it is next day for KK
so book the tickets in this way and search if seats are available
Also...
more... if you get confirmed ticket till gulburga you can pay excess fare to the TT and travel till kopargaon normally lot of people travel this way
Further more optiosns you can try
bangalore to daund and then pay excess fare to TT up to kopargoan