Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
If Target.Column = 1 And Target.Value = "+" Then
    Target.EntireRow.Select
    Selection.Copy
    Selection.Insert Shift:=xlDown
    Cells(Target.Row - 1, Target.Column).Value = "-"
    Cells(Target.Row - 1, Target.Column + 1).Select
    Cancel = True
End If
End Sub