If Then couldn't work

I am trying to do a if statment so if it equals to 'Mils' then it will do the calculation. But nothing is happen currently. I want to know whats wrong with my code.

z = Sheet2.range("B20").value
If z = "Mils" Then
Set cx = Sheet8.range("D3", Sheet8.range("D3").End(xlDown))
For Each rng In cx
rng.value = rng.value / y
Next rng
Set cy = Sheet8.range("E3", Sheet8.range("E3").End(xlDown))
For Each rngy In cy
rngy.value = rngy.value / y
Next rngy
End If