How get custom action paramter from BPMinbox

Hello   Everyone

     I  am  used   two custom  action in  task .  In  BPMinbox  When I click on the custom action button, enter an examination and approval.

now  I need to get this parameter,but I don't know how to get this parameter 。BPMAPI is no message about this parameter.

who   can  tell  me   about this  paramter  any  Information。