At the top of the model document, you can see these instructions:
(* variable for type of document *)
TEXT document_type := "Letter"
(* EXTRA parameter for dynamic labeling *)
EXTRA TEXT label LEN(10) VALUES("'Label A' 'Label B'")
(* Set page properties *)
#@(pagestyle(label; document_type))#
The variable document_type contains the name of the document type. The EXTRA variable with the name label creates the question that is presented in the online form when you Test the ITP Model, refer tot the picture in topic The Model Document. When you select a label and click OK, the selected value is accessible through the variable label.
Next, you see the function pagestyle being used. Notice how the result of the function is produced as output in the result document. Make sure it is the very first thing that is produced as output. The two variables mentioned earlier are passed as parameters. Refer to the Model Developer's Help for more information on the function pagestyle.