iPhone - Dictaphone - Headphones

Hi,

I need to record some phone calls from my uni for a course.

The current setup I have is clipping an external mic to one headphone which then captures both sides of the call, but this is poor as it struggles to catch the headphone due to the lack of volume.

My solution if possible, would be to have a wire to plug into the iPhone which the headphones plug in to, but have a spur off that which captures the audio out and the mic in, this then plugs in to the dictaphone allowing top notch recordings.

My question is, does a cable like this exist? Can it be made? Can it be made to work with the iPhone and headphones?

I hope this is the right place for this, if not, please point me in the right direction.

Regards,
David.