Interfacing PC sound card to mobile Phone

I need to connect mobile phone speaker out to PC mic in PC
and PCs speaker out to phones mic to establich bothway communication bitween SIP phone and mobile phone.

I m trying to foward SIP phone (soft phone) call to my mobile phone

Im using Nokia N70

I m not sure about input and output impedances and voltages of these.
whether thay match or not.

If you have some experiance of this please advice me

Ham Radio enthusiasts do this all the time when interfacing their transceivers to computers to engage in various digital modes. There is a variety of DIY info out there like this, or there are lots of commercial products, too.