How to lock the trunk for valet parking

[s420]

95 S420

Is there a way to lock the trunk for valet parking?

If I lock the trunk with the key, it locks up the door of the car, so the valet cannot get into the car. that's no good for the valet. If I don't lock the car, than the trunk can be opened with the button on the dashboard.

I heard from somebody that there might be a button somewhere like in the glove compartment to lock the trunk.

thanks a lot