Make the hidden parameter the timestamp when the web page was generated. Have an empty, web-writable file for each button on the page. When you get a button push, compare the hidden field to the timestamp on that button's file. If the time stamp is between that timestamp and "now", then honor the request and "touch" that button's file (update the file's timestamp). If the timestamp is too old, don't honor the request and respond saying that that resource was recently change so their change was ignored. If the timestamp is in the future, complain and "do something appropriate".

Note that this also has the benefit of preventing me from updating an item that my web page says should be updated but that Adam update while I was looking at my page. This is probably a good thing.

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