En la hoja donde tienes la celda a validar, le das click derecho en "ver codigo", insertas este codigo
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Address <> "$E$1" Then Exit Sub
If Evaluate("SUMPRODUCT( --ISNUMBER( SEARCH({""1"",""2"",""3"",""4"",""5"",""6"",""7"",""8"",""9"",""""""""}, E1) ) )") > 0 Then
With Application
.EnableEvents = False
.Undo
.EnableEvents = True
End With
End If
End Sub
asi no se podra insertar ningun numero en esa celda
nota: en este ejemplo "E1"