Motorola A630

Does anyone know if its possible to lock the keypad on the A630 while in a call. My Nokia 3108 had this function and it made it convenient to place my phone back in the case/holder on my hip and not press any buttons. I haven't found this on the A630 and wondered if it were possible. If not, I may just get another case that hold the phone horizontally instead of vertically.

thanks in advance.