my lock button has broken. can I lock my phone in other way until I fix my button? if I lock it using A key, I have to take out the battery so it will restart and I can use it again. And it's kind of frustrating....

If you mean the mute key no but the convenience key can be set for password lock. See if it will do what you want.

If you have a device password, pressing ALT+Return will lock the device.

I know the Alt-Return key will lock it but the OP seemed to be looking for an alternate method to unlock the keypad....at least i think he was. Maybe