u can not make a telescopic ticket in same train.
u have to take two separate ticket.
like if from chennai to howrah in coromondol exp is waiting list and if it is available from chennai to VSKP and VSKP to HWH than u can book two ticket from MAS- VSKP and VSKP - HWH by paying separate fare for both tkt. But no direct ticket from CHENNAI to HOWRAH resv up to VSKP and in same train again reservation from VSKP to HWH.