Yes, and something that may not even be possible. Every cable has a maximum data transfer speed, and unless 3.5 mm and VGA have a similar transfer speed, it wouldn't be possible. It would also require quite a bit of soldering.
I have done this... Audio passed through flawlessly. The huge soldering job, and opening your new tv voiding the warranty, make it a rather outrageous option. But I'll do just about anything for money, and at 50 bucks an hour, that put a neat 250 bones in my wallet.
But as to the OPs problem, the best option will be to skip the TVs audio all together... the speakers in most tvs will not perform at nearly the level of even a midrange computer speaker package, or HTIB... Just run the audio from the computer to the computer speakers or stereo unit... Prepare for rockage!
@ DEFRON, remember that most TVs utilize a PC AUDIO port when taking video through a VGA input... Selecting the VGA input then disassociates the other audio inputs on the set. Thus the need for the 1/8th inch audio patch.