May be used to specify an Extended virtual function key code (see appendix) to generate a unique exitcode when the XTREE control is clicked while inactive (e.g. "VK_Xf401"). Note that when clicking on an inactive XTREE, the row clicked on is automatically passed to the XTREE control so that it can select that row, rather than the first row. For single-selection XTREEs, in order for this to work, you must set answer=0. (Otherwise, the specified ANSWER will override the clicked row to determine the new selection.) For multi-selection XTREEs, the clicked on row will be added to the existing selections.

The XTRA4 program in the SOSLIB program illustrates this.