Adding specific data depending on previous column cell value

Need help with the following:

I HAve colums with Ip addresses can be random and want to add in next column the location of IP address .
eg


10.70.60.10
10.70.50.25
10.70.50.26 etc

then run a macro that will add in the next colums the location

10.70.60.10 Building A
10.70.50.25 Building B
10.70.50.26 Building B etc

Thanks

How do you know which IP address located in which building? the Macro is easy, but we need to know the connection between the IP Address and Building tag.

I guess the Building tag depends on the 3rd part of the IP address, that means for all the IP Address which the 3rd octet is 60, they are located in Building A, and for 50 in Building B. Is this right? (usually the subnet mask will be more convenience.)