Bonjour,
une solution via une macro.
Sub quadrillage()
nl = Cells(Rows.Count, 1).End(xlUp).Row
nc = 15
i = 4
pl = i
While i <= nl
If Cells(i, 1) <> "" Then
For j = 1 To nc
With Range(Cells(pl, j), Cells(i, j))
.Borders(xlEdgeLeft).Weight = xlThin
.Borders(xlEdgeTop).Weight = xlThin
.Borders(xlEdgeBottom).Weight = xlThin
.Borders(xlEdgeRight).Weight = xlThin
End With
Next j
i = i + 1
pl = i
Else
i = i + 1
End If
Wend
End Sub