<%'=================判断学号是否为数字====================


<script language=vbscript runat=server>
for i=1 to len(trim(studentnumber.value))
c=mid(studentnumber.value),i,1)
if not(c>"0" and c<"9")then
alert("请输入数字！")
studentnumber.focus()
studentnumber.select()
exit for
else
Response.write "你的输入正确！"
end if
next
</script>
%>

请高手告诉我错误是什么啊