Sub Calcule()
Dim L%, C%, Colonne%, Diff
Application.ScreenUpdating = False
DL = Range("A65500").End(xlUp).Row
DC = Cells(1, Columns.Count).End(xlToLeft).Column
Range("B2:Z1000").ClearContents
For L = 2 To DL
Diff = 9 ^ 9
For C = 2 To DC
If Abs(Cells(L, 1) - Cells(1, C)) <= Diff Then
Diff = Abs(Cells(L, 1) - Cells(1, C))
Colonne = C
End If
Next C
Cells(L, Colonne) = "X"
Next L
End Sub