能不能给句体解释一下，这里还有个错误，请给改一下，谢谢
<%
response.buffer=true
formsize=request.totalbytes
formdata=request.binaryread(formsize)
bncrlf=chrB(13) & chrB(10)
divider=leftB(formdata,clng(instrb(formdata,bncrlf))-1)
datastart=instrb(formdata,bncrlf & bncrlf)+4
dataend=instrb(datastart+1,formdata,divider)-datastart
mydata=midb(formdata,datastart,dataend)

set connGraph=server.CreateObject("ADODB.connection")
connGraph.ConnectionString="driver={Microsoft Access Driver (*.mdb)};DBQ=" & server.MapPath("images.mdb") & ";uid=;PWD=;"
connGraph.Open

set rec=server.createobject("ADODB.recordset")
rec.Open "SELECT * FROM [images] where id is null",connGraph,1,3
rec.addnew
rec("img").appendchunk mydata
rec.update
rec.close
set rec=nothing
set connGraph=nothing
%>