In either case:
'Compliments of
'Ron Rosenfeld Apr 8 2003, 4:28 am
Private Sub Worksheet_Change(ByVal Target As Range)
Application.EnableEvents = False
Dim c As Range, aoi As Range
Set aoi = [A1

10] 'range to make all negative numbers
For Each c In aoi
If Len(c.Text) > 0 Then 'Is anything there?
If Not Left(c.Formula, 1) = "=" Then 'ignore if a formula
If IsNumeric(c.Value) Then 'make sure it's a number
c.Value = -Abs(c.Value)
End If
End If
End If
Next c
Application.EnableEvents = True
End Sub