Option Explicit
Sub Nom_prénom_séparer()
Application.ScreenUpdating = 0
Columns("a:b").Insert
Columns(3).SpecialCells(xlCellTypeConstants, 23).Copy Destination:=Range("a1:b1")
Columns(1).Replace What:=" *", Replacement:=""
Columns(2).Replace What:="* ", Replacement:=""
Columns(3).Delete
Application.ScreenUpdating = -1
End Sub