It'd take a bit of python or scripting work, and I'm not exactly sure about what the script would need to look like to be efficient, but you could potentially write an external lookup for this. There's a generic example about how this works in the docs, and an example script that ships with Splunk
The idea is you have a single external lookup for splunk that takes csvfileIndex and surname and the script upon invocation dynamically retrieves addresses from the appropriate file(s), then your search is easy. (The script to accomplish this however...)
... View more