Send notification to email list based on other column with the same value

[romanus]

I am trying to send a new comment notification (Comment4) to users (User1,User2,User3) of the same article title:

Title User   Comment
A     User1  Comment1
A     User2  Comment2
A     User1  Comment3
A     User3  Comment4

In the To (Email list for workflow rule) for single row I write expression LOOKUP([_THISROW].[User], Users, ID, Email), but how to list email based on the other column with same article title?