How to: free text cell, that can also assume a value depending on other cell?

Try:

Private Sub Worksheet_Change(ByVal Target As Range)

' The goal is to have C9 affected by E9,
' but also C40 by E40, C71 by E71,
' C102 by E102 and C133 by E133.

' Define and set the "range of interest" = cell E9
Dim rInterest As Range
Set rInterest = Me.Range("E9, E40, E71, E102, E133")

You shouldn't need to change anything else.