Rolling Dates in a report

Hello.  

I have a project sheet to track individual projects.  Each project is a separate row in the sheet, with a Start date, a Duration and a calculated Finish date.  New projects (new rows) are added to the sheet via a form that that can be used by anyone from our web page.  When the for form is submitted with a new project, a new row is added to the project sheet.  

I provide visibility of the projects through a report on a dashboard.  I would like to the report to only pull projects that have a 6 month moving window.  I would like to identify all projects that are submitted, starting or finishing during the past 90 and the future 90 days.  

I know the Report Builder allows you to select Finished dates in the last 90 days, or Finished days i the next 90 days, but it will not allow you to do both. The same applies for using the start date.  

I hope this makes sense. Thanks for any help.

Tim Jensen