Land Rover Repair: key remote, land rover discovery, handset code

Question
hello and thanks for your time.
My red light was steady on my 2001 land rover discovery key remote and it would not allow me to lock/unlock doors...so I went to the store and bought a new battery for it. The steady light disappeared but I still cannot lock and unlock doors OR start my car anymore. Does the key need reprogramming or is there a simple way to do it.... ie, insert key in door and push unlock and lock etc?? Or is there a bigger problem behind this? My truck is in the parking lot of the store I bought the battery from :(
When I insert the key into door, my car does lock and unlock....just not from the remote.
thanks again for helping me out!

Answer
Sorry for the delay in answering, I wanted to double check my answer.  Unfortunately, as I suspected, if the vehicle was locked and armed when you changed th remote battery, you cannot re-code the handset without the remote handset code, which in most instances is long lost.  If you do not have your code, you can have your car towed to the dealer and they can disarm it with the emergency key access code for your vehicle.  Once disarmed, you can buy a new handset or choose to use just your door key and forgo the alarm system.