FUNCTION

Four possibilities exist for a listviews multi select capabilities:

MUIV_Listview_MultiSelect_None:
The listview cannot multiselect at all.

MUIV_Listview_MultiSelect_Default:
The multi select type (with or without shift) depends on the users preferences setting.

MUIV_Listview_MultiSelect_Shifted:
Overrides the users prefs, multi selecting only together with shift key.

MUIV_Listview_MultiSelect_Always:
Overrides the users prefs, multi selecting without shift key.

Please do not override the users prefs unless you have a good reason!