I am trying to build a process that will automatically add a picklist value from a multi-picklist field if certain other fields have data. So if field A is not blank, add XYZ to the multi picklist in field B. I got it to where it will change the value to XYZ, but not keep the other values already list. I need to it to keep the values already there, and just add XYZ. Any help is appreciated. #Multi-picklist Field ##Process Builder
Eric Praud (Activ8 Solar Energies) 
Forum Ambassador
Hi Cindy,
MS Picklists are a real pain to work with...
I've used a workaround before with a little help from @Steve Molis:
Create a Long Text Area field on the object (doesn't need to be on the page layout)
In the process builder, keep your criteria.
Add a record update for the record that triggered the process and select:
Field: Long Text Area Field
Type: Field Reference
Value: [Object__c].MS_Picklist__c
Add a second record update for the record that triggered the process and select:
Field: MS Picklist
Type: Formula
Value: [Object__c].LongTextArea__c+";X;Y;Z"
Save and activate
