Much better
It depends if you want to just connect audio or audio and video and if you want to tap into a cable that you are already using for scart.
Audio and video 1)
Im no expert but a quick google search for 'Scart Pinout' gave me the following page:
http://www.diyha.co.uk/electronics/scart.html
From that diagram pin 1 ia audio output right, pin 3 is audio ouput left and pin 4 is audio ground.
Chop one end of a scart lead and use a multimeter to find which pins are 1, 3 and 4.
I googled for 3.5mm pinout and got the following page:
http://pinouts.ru/Home/Tele35s_pinout.shtml
Chop the end of a 3.5mm stereo cable and find which wires are L, R and ground and then attach these to the appropriate wires of the scart cable.
Reattach the other scart>scart wires.
Alternitevely get scart cables and chop one in half to find out which wires are which and then just cut the insulation of the second scart cable and then hack the wires that you identified from the first scart cable.
Audio 1)
Do the same as above but dont reconnect the other tv signal wires. (However im not sure if the TV will function if all the scart wires are not connected)
Your other option would be to use a composite scart adapter like this:

Obviously you would need to use s-video for the video signal.
Im not 100% sure the above would work but I would enjoy finding out if it did

Edit: Beaten to it!!