Hi,
   <!– Checkin document –>
         <action id="checkin_doc">
            <evaluator>org.alfresco.web.action.evaluator.CheckinDocEvaluator</evaluator>
            <label-id>checkin</label-id>
            <image>/images/icons/CheckIn_icon.gif</image>
            <action-listener>#{CheckinCheckoutDialog.setupContentAction}</action-listener>
            <action>dialog:checkinFile</action>
            <params>
               <param name="id">#{actionContext.id}</param>
            </params>
         </action>
Change the action listener implemetation to put your custom logic.
Thanks,
Patil
Cignex Technologies
Bangalore