Put <enter> in those cells to begin, and then add

Private Sub Worksheet_Change(ByVal Target As Range)
Const WS_RANGE As String = "G1,H5,K6,L10" '<=== change to suit

   On Error GoTo ws_exit
   Application.EnableEvents = False
   If Not Intersect(Target, rang(WS_RANGE)) Is Nothing Then
       If Target.Value = "" Then
           Target.Value = "<enter>"
       End If
   End If

ws_exit:
   Application.EnableEvents = True
End Sub

This is worksheet event code, which means that it needs to be
placed in the appropriate worksheet code module, not a standard
code module. To do this, right-click on the sheet tab, select
the View Code option from the menu, and paste the code in.

--

HTH

Bob Phillips

(replace xxxx in the email address with gmail if mailing direct)