This is a modification of one of Bernie Deitrick's replies earlier this week
Copy the code below, right-click the sheet tab, select "View Code" and paste
the code into the
window that appears.
Change the
Set rngPCode = Range("D

")
to the column where the numbers to be negated (!!) will be entered.
Private Sub Worksheet_Change(ByVal Target As Range)
Dim rngPCode As Range
Set rngPCode = Range("D

")
If Intersect(rngPCode, Target) Is Nothing Then Exit Sub
If Target.Cells.Count > 1 Then Exit Sub
On Error GoTo Reset
Application.EnableEvents = False
If (Mid(Target.Value, 1, 1) = "-") Then
Target.Value = Target.Value
Else
Target.Value = Target.Value * -1
End If
Reset:
Application.EnableEvents = True
End Sub
best wishes