immobiliser or key

Hi, I have had the key battery low message come up on the dash for my main key (normal VW group flip key). Instead of replacing it I just used my spare key. Then my spare key battery became low and the same message came on the dash. I bought replacement CR2025 batteries for both keys. I firstly...

i have a new flip key fob that is cut and programmed so that it opens the doors etc (remote works) but i need the immobiliser reprogrmmed , im booked in at the dealers next week , but was wondering can i do this with vagcom ( have full version) i read a guide somewere that i need a dealer code...