Sub test()
Dim sh As Worksheet, col As Long
For Each sh In ThisWorkbook.Worksheets
sh.Activate
For col = 1 To 26
With ActiveSheet
If .Cells(1, col) = "Temps" Or .Cells(1, col) = "Velo" Then
.Columns(col).Name = .Name & "_" & .Cells(1, col)
End If
End With
Next col
Next sh
End Sub