Hello Dan. Thanks for answer me.
I'm Jose Enrique and I'm writing from my home.

I dont't remember exactly the code because I'm not in the office but I try
to write you the code I remember. Nex monday I write you the exact code: Do
you find any error?

Global process:

While not g_bFin ( the g_bFin variable will be False when the user stop the
service. My program is a NT Service)
   For i=0 to iUsers-1
       bCheck = bCheckMailbox(ExchangeAlias(i))
   next
   lTime = Timer
   While Timer <= lTime + 30000
       DoEvents
   Wend
Wend

I don't remember exactly de code - the new monday I write you the exact
code:

Function bCheckMailBox(BVal cAlias as string)  as Boolean

   (variables declaration)
   ....

   On Error Goto ErrorPoint:

   Set ObjSesion = new Session
   ObSesion.Logon cAlias
   Set ObjCalendar =
objSession.GetDefaultFolder(MAPI.CdoDefaultFolderCalendar)
   Set ObjColAppointments =  objCalendar.Messages
   Set ObjFilter = ObjColAppointments.Filter
   objFilter.Fields.Add CdoPR_START_DATE, Now-7
   objFilter.Fields.Add CdoPR_END_DATE, Now+7

   cNow = Format$(Now,"yyyymmdd hhnnss")
   For each ObjAppointment in ObjColAppointments
       cState =  ObjAppointment.BusyStatus
       cStartDate = Format$(ObjAppointmen.StartDate,"yyyymmdd hhnnss")
       cEndDate = Format$(ObjAppointment.EndDate,"yyyymmdd hhnnss")
       If cStartDate <= cNow And cEndDate>=Now then
           cUserState = cState
           cUserStart  = cStartDate
           cUserEnd = cEndDate
           Exit for
       endIf
   Next
   Set ObjCalendar = Nothing
   Set objColAppointments = Nothing
   Set ObjFilter = Nothing
   ObjSession.Logout

   bCheckMailBox = True

   Exit Function

ErrorPoint:
   bCheckMailBox = False
   Set ObjCalendar = Nothing
   Set objColAppointments = Nothing
   Set ObjFilter = Nothing
   ObjSession.Logout
End Function