code to insert dash sign

Replace all the code in the sheet module with this:

Option Explicit
Public Prior As String

Private Sub Worksheet_SelectionChange(ByVal Target As Range)

    If Target.Column = 6 Then Prior = Target.Text

End Sub

Private Sub Worksheet_Change(ByVal Target As Range)
Dim cell As Range

For Each cell In Target
    If cell.Column = 6 Then
        Select Case cell.Value
            Case "Company", "Organization", "School", "S. S. C. board"
                Application.EnableEvents = False
                Range("Q" & cell.Row).Resize(, 9).Value = "-"
                Application.EnableEvents = True
            Case Else
                Select Case Prior
                    Case "Company", "Organization", "School", "S. S. C. board"
                        Application.EnableEvents = False
                        Range("Q" & cell.Row).Resize(, 9).Value = ""
                        Application.EnableEvents = True
                    Case Else
                        'do nothing
                End Select
        End Select
    End If
Next cell

End Sub