There's no need for you to use an array. I assume this is a homework question, since you explicitly want to find out how to locate the smallest number using a loop... You can get it directly from the database by using the min() function.
Here's a code snippet for how to go about it - you will need to pad it out as required.
sn = rs("xyz")
rs.movenext
do while not rs.eof
if sn < rs("xyz") then
sn = rs("xyz")
end if
rs.movenext
loop