calling from Activity

Hello

I am not able to communicate from activity i.e. I have a Main activity which active another Activity (which generate a multiwidget form) and I would manage some events by main Activity, so in Main I have something like this (is only the last of my tries):

Sub handleChange3(wdg As Object,parms() As Object) As String
If parms(0) = "Dollar" Then
Dim txt As EditText
txt = wdg
Msgbox("Dollar: " & txt.Text,"")
End If
End Sub

Msgbox crashes on Null pointer exception.

In the calling activity I have:

Sub txt_FocusChanged (HasFocus As Boolean)
If Not(HasFocus) Then
fh_sender = Sender
Log("*************** " & fh_sender)
CallSub3(fh_externalCaller,"handleChange3",Sender,Array As Object ("Dollar","","LF"))
End If
End Sub


Besides I have discovered that if the activity is not active, from its Functions we do not have access to global variables of the Activity active, is this correct?

Thanks

John Rossati