Need to copy value in one field to another when a status field changes all within the same record

Of course! I appreciate the help - 

I have a parent table called Projects that has a child table called Ops

-The Projects table has a field called Status, this field can either have the value "Not Started" or "In-Progress"
-The Ops table has a field called Actual Start and another field called Planned Start
-When I change the Status field in the Projects table from "Not Started" to "In-Progress", I want the value in the Actual Start field in the Ops Table to populate the Planned Start field also in the Ops Table, for each Op related to said Project.




The Automation that I am trying looks like this:

Trigger: When a user modifies a record in the Projects table <and> Status changes <and> Status is equal to the value "In-Progress"

Action: Modify records in the Ops table where Related Project ID# is equal to the value Project ID#, populate the field Planned Start in Ops > Value from another record > (I only see fields from the Projects table to select here, I need the field being copied from to be the Actual Start field from the Ops table




I tried to work around this by creating a Project Status Lookup field in the Ops table, then changed the Automation to:

Trigger: When a user modifies a record in the Ops table <and> Module Status changes <and> Module Status is equal to the value "In-Progress"

Action: Modify records in the Ops table where OP ID# is equal to the value OP ID#, populate the field Planned Start in Ops > Value from another record > Actual Start in Ops

This seems to me like it should work, but the action doesn't even run - I'm assuming this is because a user (me) isn't actually modifying any records in Ops, it's just the lookup field Module Status in Ops changing to match the "In-Progress" value in the Status field in Projects

It seems like this would be easy to do - am I missing something really simple?