One option once you've entered all the numbers as positive is to put -1 in a
spare cell, select and copy, the select your column, edit/ paste special/
multiply.

If you just want that column to display as if they were negative numbers,
you could format as "-"General, and then when you want to do calculations
from that column you could subtract instead of adding.

Mon, 3 Sep 2007 01:50:07 -0700 from DeeDeeCee
<DeeDeeCee@discussions.microsoft.com>:

Yes, with custom formatting, but I recommend against it. When you see
a column of negative numbers, sooner or later you'll type a minus
sign in front of one of them and then your computation will give a
wrong result.

I know I'm a day late here but if you're still watching............

You could use event code to change the typed numbers to real negatives as you
enter them.

Private Sub Worksheet_Change(ByVal Target As Excel.Range)
'change a number to negative
      If Target.Column <> 2 Then Exit Sub
      If Not IsNumeric(Target.Value) Then Exit Sub
      If Not Left(Target.Value, 1) = "-" Then
    Application.EnableEvents = False
    With Target
        .Value = .Value * -1
       End With
End If
Application.EnableEvents = True
End Sub

This is sheet event code.  Right-click on the sheet tab and "View Code".

Copy/paste into that sheet module.

As written it operates on column 2(B) only.  Adjust to suit column number.

Gord Dibben  MS Excel MVP