Originally Posted by m3red

You need to do an advanced search and do

HKG DXB
DXB LYS

LYS HKG

assuming you want to stop on the outbound.

Originally Posted by skywardhunter

outbound would be HKG - LYS and OP had mentioned that's when he wants it. But yes, as m3red pointed out, do a multi-city/advanced search as:

HKG - DXB
DXB - LYS
LYS - HKG with the appropriate stopover dates.