How to search for members using IP wildcards? (12.34.56.*)

[MartyMcFly]

We are using IPB4 and would like to find members that keep changing IP addresses but within the same subnet.

For example they will begin posting using 12.34.56.100, get banned, and then re-register using 12.34.56.200.

My question is, how can we find all members using an IP wildcard search such as 12.34.56.*? Using 12.34.56.* as the search term does not appear to work.