If you want all headers removed, go to report->and uncheck "show all headers on drilldown". Otherwise, depending upon your version (which you should ALWAYS identify), you can use the drilldowngrouplevel function to conditionally suppress headers depending upon level of drilldown, e.g.,
drilldowngrouplevel > 0 //suppress this header during drilldown
Each incremented number represents another drilldown level.
-LB