Private Sub Worksheet_Change(ByVal Target As Range)
Dim P As Range, cible$, L%, x$, i%
Set P = Range("A2:A" & UsedRange.Rows.Count) 'plage à étudier, à adapter
If Intersect(Target, [C1]) Is Nothing Then Set Target = Intersect(Target, P) Else Set Target = P
If Target Is Nothing Then Exit Sub
cible = [C1]
L = Len(cible)
Application.ScreenUpdating = False
With Target.Font
.ColorIndex = xlAutomatic 'RAZ
.Bold = False 'RAZ
End With
For Each Target In Target 'si entrées ou effacements multiples (copier-coller)
x = Target
For i = 1 To Len(x)
If Mid(x, i, L) = cible Then
With Target.Characters(i, L).Font
.Color = vbRed 'rouge
.Bold = True 'gras
End With
End If
Next i, Target
End Sub