A handheld electronic device useful for wireless communication has a keyboard including a plurality of externally accessible keys and each key has at most, one letter associated therewith. The keys can be disabled (i.e. the keyboard can be locked) to prevent accidental actuation thereof by using the navigation tool which has a depressible rolling member. Thus, for example, depression of the rolling member twice in succession or pressing and holding the rolling member down temporarily enables the keyboard lock. The lock can be disabled simply by depressing the rolling member and at least one other key.