>In an array, I have a definition of the fields of my table. So, the first row contains all the field names. When I use ASCAN to find a specific field name, it will locate the proper row. However, assuming I want to search for field name NOM and that I have another field NOMEMBER which is placed before NOM in the array, NOMEMBER will be found before NOM. How can I force ASCAN to be precise?

If SET EXACT is OFF then your ASCAN is operating completely normally. It's nice that you can control it at the level of the function, though, 7.0.