Hi Russ! Thank you very much for the help.

I'm studying the links you showing me, but the code that I'm reading in the
second link, doesn't works:
Dim X As New EventClassModule
Sub Register_Event_Handler()
   Set X.App = Word.Application
End Sub

I'm developing an Word Addin using VB .NET and the "Set" keyword, doesn't
exists; when I paste that code in the developing enviroment, the "Set"
keyword disappear, I'm developing a word addin, maybe that code refers to VBA
language.

Anyway,
this is the code I've put in the DocumentBeforePrint Sub in my Word Addin:

      Try

               MsgBox("Hello World!")
               Cancel = True
       
       Catch ex As Exception
           MsgBox(ex.ToString)
       End Try

I set "Cancel" to TRUE becouse I read this:

Cancel-   False when the event occurs. If the event procedure sets this
argument to True, the document isn't printed when the procedure is finished.

So I think I should see the MSGBOX "HelloWorld" and I can't see the window
for Print the Document...it's not true! I can see the MSGBOX and I can see
the window for Print and I can print the active document.

Have you a workaround for my problem?

thank you