Turnbuckle with symmetric slider constraint

Hi,

I have assembled a turnbuckle and I have placed the two spindles with 'slider' constraints. However, I would like both spindles to move symmetrically related to the body of the turnbuckle when one spindle is dragged. I thought that it was possible to create a relation that would make the distance from the body of the turnbuckle to the spindle half of the extension.

Does anyone have experience with this?

Regards

Niels