Here are the steps you need to take to make the change:
1. Go to step 3 of 9 within the Grid Wizard.
2. Click on New/Edit and make it a new view
3. Select the field that you want to filter by
4. Click on Insert Filter
5. Select the filter criteria for that field
In addition to the above steps, you will need to use actions outside of the grid to get the 7 days before date. This can be accomplished by creating an action on screen load that will get the current date - 7 days and load the date onto a hidden field on the screen.
I hope that helps.