Just remove or comment out 'option explicit'.
Difference of opinion here, but I'd leave it in, but Dim sn correctly (and Dim the other variables as well of course.) Without the OE and Dim- everything is a Variant

Variants take longer and use more memory, and don't allow proper Type checking (i.e. only Longs into a Long) to avoid errors. I prefer (again personal opinion) to use Variants sparingly and only when absolutely needed

Most likely it should be 

Dim sn as Variant
Next week's topic: Using meaningful names for variables