Defining your own searchhelp for a table column: In the VA01 item table we have a column that corresponds to a particular attribute of the classification system.  I would like to implement a special search help for this column. Is this possible with GuiXT?

Yes, you can do this with the Searchhelp command; it allows us to add a searchhelp for a given table column. With the notation searchhelp="exit...." you can then implement a special searchhelp via an ABAP exit function. For details see the examples in the "InputField" documentation, section "Programmed matchcode help".