Email Notifications when custom field doesn't match trigger user name

[Kevin Shiflet]

I have set up a rule on our Trello boards driven by a custom field 'Currently Assigned to'. When the field is set to a value, Butler looks through to a matching card on a Directory board and sends an email notification to the relevant email address for that coworker. 

It works well enough, but I'm trying to tighten it up so that if you set it as Currently Assigned to yourself you DO NOT get a notification. 

Does anyone have any experience with this? I poked around a bit but nothing seems to fit. I'm thinking it would be something along the lines of 'If custom field X is set to a value NOT matching the triggerusername'. 

Automation language is below. 

when custom field "Currently Assigned to" is set, find a card titled "{{%Currently Assigned to}}" on board "Directory", and send an email notification to "{{%EmailAddress}}" with subject "{triggercardname} on {boardname} was reassigned to you by {fullname}" and message "Board Name: [{boardname}]({boardlink})\n\nReassigned Card: [{triggercardname}]({triggercardlink})\n\nReassigned to you by:{fullname} \n\nDescription:[{triggercarddescription}] \n\nCard Due Date: {triggercardduedate}\n\n\n{$report_html}"

[Mike - Dreamsuite Consulting]

I hope this is a simple fix, change the first line to:

when custom field "Currently Assigned to" is set, find a card titled "{customfieldvalue}"