I can't give you a direct answer. However, you're not alone in looking for such answers. Your problem is really the old TV. There are so many variables and issues in dealing with such adaptions, they are all too unique and when dealing with old stuff, best to walk away, IMHO.
That DVD to TV then the laptop, that's may require a RF switch or maybe not. If you've got video then you need the audio portion, is there a audio port? if not, you found your problem. Cabling, itself poses a problem as you may need to go RCA type connector or plain strip wire and screw down if needed. Sorry, it gets too involved. I suggest you google away and see how "cable TV and/or satellite" connections are made to get an idea of what may work even not your situation, the devices/paths used could render a solution.
I want to connect my laptop to an old tv that does not have s video cable port. I do have a dvd player that is connect to the tv that has a s video port. Can I connect my laptop to dvd which is connected to tv? and what do I need to do for sound?