HdrClickExit=###
When specified, clicking on this column header causes an exit with the specified exitcode. It returns the XTR.COLUMNSORT and XTR.SORTORDER fields as if a sort had taken place, but it doesn't actually sort.
The intent is to allow applications to implement their own sort logic.
Note that when HdrClickExit=### is defined for a column, that column will not be sorted on entry even if the column appears in the initial XTR.COLUMNSORT array. If you want subsequent clicks on the column header to toggle between ascending and descending, you must leave the XTR.COLUMNSORT set to the specified column on re-entry. Otherwise the initial sort for any unsorted column will always be ascending.
