Replaced battery in remote key and now won't unlock/lock car

Hi,

I have a 2008 535i that indicated (on the IP) that my key remote was running out of charge/discharging. I placed the remote in the ignition lock while driving long distances to keep it charged (doing this for several weeks) , but still continued getting the message that the key was discharged/discharging when I recently tried to start my car without the key in the ignition lock. I am also having trouble unlocking/locking my car with the remote, in general. Comfort access hasn't worked in a while.

Looked in the manual to see how to replace the battery, which I did replace, but now, my remote will not lock/unlock the doors whatsoever, although the car does start up without the key in the ignition lock.
Called my BMW dealer who advised me it would cost $140 to reprogram the remote.

Was wondering if there was any way to program it on my own?

Thanks