How to lock handset during call for hands-free use?

[sidewalking]

I can't find this in any searches...Is there a way to lock the myTouch 3G handset during call for hands-free (Bluetooth) use? I would like to pocket it or put it in it's holster case during a call, but would need to lock it to prevent hanging up on the call. However, apart from the screen lock, I don't see a way to lock the phone buttons without using the "End Call" button...which ends the call (of course).

Is this possible with this particular phone?

 

[pyehac]

If I recall, the screen will automatically lock while on a call on the headset - I don't know if that's the case while on a bluetooth headset, as I use a belt holster and just holster it while using the headset (yeah, I'm that person who talks to himself in the malls - its easier than just using the phone itself)