Yes, we do this pretty frequently.
in teh pre-process tab compute the date you pant to plug in.
in my example its the last day of the previous period.
:set &today = sys_ldate()
:set &topodate# = sub_days(&today,0,CALE.RALCORP,LAST_DAY_OF_PERIOD)
:set &topodate# = conv_date(&topodate#,'MM/DD/YYYY')
you then plug the variable name (&topodate# in my example) in the right operand of the data selection or processing option override.
I recommend you set generate at run time on the attributes tab if you do this.