Sub test()
Dim n As Long, x As Long
n = 1' valeur de n arbitraire pour tester la macro
x = n + 3
'mon écriture
MsgBox Union(Range("Q5").Resize(x), Range("V5:X5").Resize(x)).Address
'l'écriture de mth
MsgBox Union(Range("Q5:Q" & n + 3), Range("V5:V" & n + 3), Range("W5:W" & n + 3)).Address
End Sub