Sounds like a classic vlookup

[codyswan]

It sounds like you already have a large list of what IP addresses match with hotmail, yahoo, etc. If not, you can sort some recent lists by IP address and make a table from there. The listing with the IP addresses and corresponding providors becomes your vlookup table.

Then, next to each IP address for that day, you will have a copy of a formula something like this:

=vlookup(sheet1!:a1[containing an IP address you want to match],IPTable[which is on another sheet or in another file and reused every day],2[return second column data, the matching hotmail or yahoo],options)

I'm not sure if IP addresses are all clustered together for a particular service. If they are, set the option to match the nearest entry.

If IP addresses for a service are not clustered together, use exact matching. In that case, put the vlookup inside an IF statement. Make the IF statement return some value like "n/a" if the IP address is not in your table yet.

[codyswan]

oops, belong under allornothing's post