IN() Expression using a Parent Ref as the Source Column

[Scott_S]

I have a referenced table that I am trying to perform a Required IF expression in.

IN([Type], {“Controller Image”, “Traffic Signal”})

"When the Column [Type] which is in the main source table called "master’ has the value of “Traffic Signal” I want the column “Controller Image” to be required. This column is in a referenced table called “images”

My problem s the “Controller Image” column isn’t in the same table as the “Type” Column.

Not sure on how to write the expression