Using PC microphone as a Bluetooth headset

There is a ton of stuff re. " Bluetooth Headset as a PC Microphone".

I want to do it the other way.

I have Bluetooth on my PC and my mobile is Bluetooth enabled. I want to
use the microphone and speakers on my PC as a "Bluetooth headset". In
essence, the PC microphone replaces the Bluetooth headset.

As far as the mobile is concerned, the functionality is the same as if
I was using the Bluetooth headset.

Is there any software that I can buy that allows this?

Thanks