I am attempting to sort my leads by how many concurrent Voicemails I've gotten for a prospect (so if someone gets 6 Voicemails in a row they are a lower score than someone that's only gotten 3). I have a Lookup field called 'Call Results' which displays all the values related to a Contact's call results from the Touchpoints table like so:

Voicemail, Call Me Back, Call Me Back, Appointment Approved, Voicemail, Voicemail, Voicemail, Voicemail, Voicemail, Voicemail

The challenge I am facing is extracting the amount of HIGHEST CONCURRENT Voicemails as an integer to use for sorting. 

So for example in the example above there are 7 concurrent Voicemails as the highest amount (note I am not counting the first Voicemail since that doesn't descore a lead but higher Voicemail numbers mean a lead is going cold). 

Any input on how I can achieve my lead scoring goal or alternative approaches would be much appreciated.

Thank you!