Causes a new message to appear in the Events log.
The displayed message corresponds to the string indexed using <sIndexString> in "data/soundscripts/speechevent/eventtext.lua".

UI_AddToEventScreen("STATUS_BuildAvaliable_1")
Note: the example above is the only instance of this function found being used in the game.

<sIndexString>: an index in "eventtext.lua", which sets a localized or quoted string.