sub domain targeting hosting server , while www targeting appengine?

Currently i have setup like below

www.wianga.com -- > google.com

I want to host a blog ,in subdomain like below,

blog.wianga.com --> private hosting server

1)Is it possible?

2)if its possible then what i have to do in my DNS entries?

It is possible, you have to create a canonical name (CNAME) in your DNS zone that point to the IP of your private hosting. (Or better: do a reverse DNS lookup on the private hosting IP to know the name of the private hosting name server)

ex: blog.wianga.com CNAME ns1.private-hosting.com