It depends if the client code is providing this information. The standard GridView, for example, sets both __EVENTTARGET and __EVENTARGUMENT when a sort header link is clicked:
Request.Form["_EVENTTARGET"] contains "ctl00$MainContent$GridView1" Request.Form["_EVENTARGUMENT"] contains "Sort$id"
where the __EVENTARGUMENT contains information that this is a Sort operation, and the column to be sorted on, separated by $.
For paging the __EVENTARGUMENT value looks similar:
Request.Form["__EVENTARGUMENT"] contains "Page$2"
Note though that not all controls populate __EVENTARGUMENT on postback, so you'll have to test.