Sub Convertion()
Dim cellule As Range
dernLig = Columns("G").Rows(Rows.Count).End(xlUp).Row
If dernLig < 4 Then Exit Sub
Application.ScreenUpdating = False
Application.Calculation = xlCalculationManual
I = InStr([G4].Text, ":") > 0
For Each cellule In Range("G4:G" & dernLig)
If I Then
cellule = cellule / TimeValue("1:00")
cellule.NumberFormat = "0.00"
Else
cellule = cellule * TimeValue("1:00")
cellule.NumberFormat = "[h]:mm"
End If
Next
If I Then [G2].NumberFormat = "0.00" Else [G2].NumberFormat = "[h]:mm"
Application.Calculation = xlCalculationAutomatic
Application.ScreenUpdating = True
End Sub