Returns a list of the names of all named objects on layoutName in fileName, separated by carriage returns.
fileName - the name of an open database file (local or remote).
layoutName - the name of a layout in the specified database file.
Important  See Design functions for information about literal text parameters.
Data type returned 
Originated in 
FileMaker Pro 8.5
Layout objects without object names are not returned. If layoutName isn’t specified, then no object names are returned.
Named tab controls, grouped objects, and portal objects that contain other named objects are followed by a list of those named objects enclosed in angle brackets (<>). The angle brackets are shown even if there are no named objects contained within the named tab controls, grouped objects, or portal objects.
LayoutObjectNames ("Customers";"Data Entry") returns a list of named objects in the Customers database file that appear on the Data Entry layout.
Related topics 
Functions reference (category list)
Functions reference (alphabetical list)
About formulas
About functions
Defining calculation fields
Using operators in formulas
Naming objects