for循环中的SQL语句只更新一次

Question

if request.form("submitChange") = "site" then
    for i = 0 to UBound(arrmode)
        SQLstr = "UPDATE SCSer SET Ser_Site_Num = '" & request.form("site_to") & "' WHERE Ser_Num = '" & arrmode(i) & "'"
        conn.execute(SQLstr)
        Response.Write("SUCCESSFULLY UPDATED! " + arrmode(i))
    next
end if