Bonjour,
Sub Test()
Dim Cel As Range
Dim Position As Integer
For Each Cel In Range("B5", Range("B" & Rows.Count).End(xlUp))
Position = InStr(1, Cel, "(")
With Cel.Characters(1, Position - 1).Font
.FontStyle = "Gras"
.Size = 10
End With
Next Cel
End Sub
A+