Hard to value due to mismash of parts: Low end late 80's (?) Colnago frame, 8-speed Dura-Ace shifters, 9-speed crankset, 600 brakes, ... All nice parts, but the combination makes it attractive as a utility bike. Probably worth more separated than whole, maybe $500 ?
I've heard that Colnago Sport models were not made in the Colnago factory, they were commisioned by other builders. I have one and it is a good daily rider, mine is made from Columbus Aelle tubing and was outfitted with Gipiemme components. Mine was in need of a repaint and I paid $125 for it 7 years ago.
If you plan on selling yours, you would be best to part it out as the Dura Ace stuff is worth more than the frame.