XML : How to create a control by condition?

ALL,

Looking at this for the "Building composite widgets from template XML" I wonder if it is possible to create a control if some condition is met. As an example, I want to check a condition and if its TRUE, then create a control, otherwise don't create it.

As an example in my program code currently I do:

  #if ABC     expander = gtk_expander_new_with_mnemonics();     hbox = gtk_box_new();     gtk_pack_start( hbox, expander);