set expression in ssrs

Hi,

I have to set parameter with date and time in such a way so when ill pull report it should be from previous date to current date and specific time.

ForExample, if i select report from 03/15/2013 to 03/16/2013, report should show data from 03/1402013 4:00 pm to 03/16/2013 3:59 pm.

so how to set expression for that? It suppose to set as default value or availabe value?

Please help me for this.

Thanks

surabhi dave