how to open attachemnts in a browser and keep track of changes made to attachmnts

actually i have got a requirement......where in user will download the attachemnt...
Upon clicking on a download link, small window will be prompted automatically asking the user whether to open,save or cancel the operation..
Now if the user clics on open button, the document will be opened........is there any way we can track the changes made to the document and accordingly prompting a custom window to the user.

You don't have any control over the application the user can use to open the attachment, so no. You would need to provide an application for editing these attachments (an applet perhaps) to take the place of whatever they might normally use. Quite a big job.

Paul Sturrock wrote:You don't have any control over the application the user can use to open the attachment, so no. You would need to provide an application for editing these attachments (an applet perhaps) to take the place of whatever they might normally use. Quite a big job.

Can you just give me brief idea, regarding how this can be done using Applets?
Is there any other alternative?