MSG-TV-SELCHANGING
This event is fired when the selected item in a Tree-View control is going to be changed. The EVENT-DATA-2 data item contains the ID of the candidate item. EVENT-DATA-1 contains one of the following symbolic values, defined in isgui.def, depending on the reason of the change.
TVFLAG-MOUSE
The new item is going to be selected with the mouse.
TVFLAG-KEYBOARD
The new item is going to be selected with the keyboard.
TVFLAG-PROGRAM
The new item is going to be programmatically selected by setting the Value property.
Setting EVENT-ACTION to EVENT-ACTION-FAIL prevents the new item from being selected.