lol. how funny it is!
juz after i posed, i found ways to figure tat out..
not sure correct or not, juz for ur consideration
1. Imar somehow right, easy for all, HTTP Headers tab of the Options dialog for your Web application you'll find a Content Expiration Area. Set it to Expire immediately. as he said. do it in your IIS console, simple click then works
2. If don't wat to do it, have to say, u have to change the header for ur reporting page. Response.AddHeader "Content-Disposition","fileName=mydata.csv;"
quoted from http://www.devx.com/getHelpOn/10MinuteSolution/20482
and give me feedbacks :)
BTW, any rish to change header immediately?