This function, given a date, will return the date of the following Saturday (or Saturday, if it's Saturday).
That is, it will group any date into a seven-day "quanta" which is designated by the last day of the week (Saturday).
This will allow you to group events by week.
This is for the Sunday - Saturday week.
For the Monday - Sunday week, edit the last line:
DayOfWeek ( GetAsDate ( aDate ) - 1 )