Please go through the link below.
1. you need to use guided navigation or Condition in Section of the Dashboard page.
2.You need to create as many number of dummy reports as you want to show/hide in dashboard page.
3.Use a different section on the page for each report.
4.Dummy reports in step needs to be put in condition in step 1, and reports will only be displayed if analysis rowcount is greater than 0.
you may further do a google by show hide reports + condition + section + OBIEE page.