This works on range H1:H10, change to suit
Private Sub Worksheet_Change(ByVal Target As Range)
Const WS_RANGE As String = "H1:H10"
On Error GoTo ws_exit:
Application.EnableEvents = False
If Not Intersect(Target, Me.Range(WS_RANGE)) Is Nothing Then
With Target
If .Value > 0 Then .Value = -.Value
End With
End If
ws_exit:
Application.EnableEvents = True
End Sub
'This is worksheet event code, which means that it needs to be
'placed in the appropriate worksheet code module, not a standard
'code module. To do this, right-click on the sheet tab, select
'the View Code option from the menu, and paste the code in.
--
HTH
Bob Phillips
(remove nothere from email address if mailing direct)