Various questions about WF events

[GOURLET Gilles]

Hi all,
First of many thanks to John and Stephan for the hint regarding
authorization seeking (pgm RSUSR070).
 
I have various questions about WF events : as far as I understood, you can
only raise WF through provided business object events plus some extensions
you can make in defining status value changes.
E.g, my "custom" event is : the user status value of my business object
switch from 'A' to 'B'.
Am I right ?
So my question is : if I need to use an event that is neither one which is
provided with the standard Business Object nor a user or system status
change, what do I have to do ?
Thanks in advance,
Gilles.