If you want to go to those lengths, you can use the Format
and Parse methods of the bound control. Try this:

in Form_Load:

   'specifically bind the textbox for your field
   'you have to do this, because you need the name of
   '  the databinding in order to capture the
   '  format and parse events
   Dim myTextBoxBinding As Binding = _
     New Binding("Text", myBindingSource, "myField", True)

   'add event handlers for the format and parse events
   AddHandler myTextBoxBinding.Format, AddressOf OnMyFieldFormat
   AddHandler myTextBoxBinding.Parse, AddressOf OnMyFieldParse

   myTextBox.DataBindings.Add(myTextBoxBinding)

Private Sub OnMyFieldFormat(ByVal sender As Object, _
 ByVal e As ConvertEventArgs)
   'ConvertEventArgs contains the [Value] that is to
   '  be used for setting the bound control property
   '  unless you decide to change it.

   If e.Value Is Nothing OrElse e.Value.Equals(DBNull.Value) _
     OrElse e.Value = -999 Then
       'Show the textbox with nothing in it.
       e.Value = String.Empty
   End If

End Sub

Private Sub OnMyFieldParse(ByVal sender As Object, _
 ByVal e As ConvertEventArgs)
   'For the parse event, the Value property of the event argument
   '  contains the value of the bound control property. When
   '  the parsing process is complete, the value set on the [Value]
   '  property will be used to set the content of the bound column
   '  in the data source.

   If stringValue = String.Empty Then
       e.Value = -999
   End If
End Sub

This is *also* from Brian Noyes' Data Binding book.

Robin S.
----------------------------------------------------------
Hi

This works like a charm. Thank you.
How about if I want to display the 0 (when the value has it), but ""
when the value is fi. -999?
Basicly I want to user to be able to enter 0 and this should be
displayed. I init my properties to a default of -999 and if it is this
value, then the textbox should be empty, ie. "". Can this be done using
the formatstring argument? I haven't been able to find much info on
this parameter in MSDN.

Otherwise, thank you.