Hey everyone,
I'm pretty new to Power Apps. I think I'm trying to do something relatively simple but I'm struggling for some hours and can't seem to figure it out. I have a Sharepoint Document Library where documents are uploaded. Users can edit the column properties by the Power App form I created. Now the requirement is that if the column 'Document Status' contains value that all the fields in this Power App form should be disabled. I can't seem to access this 'Document Status' column from my Power App even though the Document Library is connected in Data:
The default values of the fields were:

A Power Automate workflow automatically populates the Document Status column in the Document Library, so the field should only be editable if the column contains no value.

The expression should probably be something like:
If(DocumentStatus=! null, DisplayMode.View, DisplayMode.Edit)
I'm looking for this behaviour:

So read/write when the column has no value and read only if it has value.
Any help is greatly appreciated!