Headphone dongle question

[juddrl]

is there some way to enable the microphone at the same time you have the dongle plugged in?

I connect a 3 1/2" cable into the dongle and the other end into the input in my car so I get the sound over my car speakers (good for pandora and navigation).

What I would like to do is use it as a speakerphone with sound over the car speakers but the dongle acts like headphones and disables the microphone.

If anyone knows, that would be great.