wmsg and lmsg are provided simply as ways for you to pass more information into your event function. If you are writing your own event function, you can ignore them entirely, or use them in any way that you see fit. There are no predefined values for these structure elements.
If you are using a Vermont Views event function, you need to check what values the Vermont Views function expects to find in wmsg and lmsg. Each Vermont Views function may use these in a slightly different manner.
