?? Help??

The other day i changed the battery on my celica for a new one, and every time i go to lock the car with the key fob the alarm goes off and i cant get it to stop with the key fob, and after a while it will stop, or it stops and then goes off again, so the only way i can lock the car is the button on the drivers door. but i can open the car ok with the key fob, but cant activate the alarm, if anyone could please help me ..

Have i got a problem or is there a way to reset it or get it working again.

Many thanks

Whiskey

P.s i have a 98 sr celica, just in case i have a different alarm system..