Not able to refer one DFF attribute from another DFF attribute

Summary:

We have a requirement to restrict the List of values for one DFF attribute at PO Header level based on another DFF attribute from PO Header.

For example, we have a enabled two attributes at PO Headers level:

1. ATTRIBUTE1 is created for Mode of Establishment (API Name: modeOfEstablishment)

2. ATTRIBUTE2 is created for Emergency Code.

Now, in the value set of ATTRIBUTE2, I am trying to add the following condition in the where condition:

:{SEGMENT.modeOfEstablishment} = '<some value>'

However, I am getting error while trying to save the value set:

"A bind variable does not refer to an existing segment or value set. (FND-2620)