[Help]About flowscript invalidation

[roy huang]

Leon mentioned in 
http://marc.theaimsgroup.com/?l=xml-cocoon-users&m=108210830729765&w=2

If I use cocoon forms I can using flowscript like:
     var k=form.showForm("display-pipeline");
     k.invalidate();
     cocoon.sendPage("ok");
When I using browser's back and sumit again,will produce :
Invalid Continuation
The continuation ID 2f0a5881335356585384513c1a4069277678515e is invalid.

You see k.invalidate() works,but can it just display the page is invalidate when I 
back ?Maybe using setHeader or something else in flowscript?

WDYT?

Roy Huang