SSRS Parameter Post backs

Most people consider parameter postbacks in SSRS as  an  unwanted operation, but some times they are necessary ,I had  a situation where i need to post back when any of the parameters is selected 

In this situtaion ,create  a   new parameter at the bottom of all parameters   and set some value like datetime as default ,one important  thing to notice is that , when  you set this  default parameter sourced from a dataset query , than this will not work,it needs to  be sourced manually  as shown below.

Irrespective of what you  select in advance parameters (as always refresh or never refresh), setting the default value as above ,will always result in post back of all  the parameters   above   this parameter ,as long as this parameter  is the  last parameter .