Two Week Rolling Date on X-Axis

[UncleRiotous]

I have a line chart which uses dates as a dimension. I can use a variable to switch between displaying in day, month or year using the following code...

=If($(vTogDayWeekMon)=1,Date(Floor(DATADATE)),
           If($(vTogDayWeekMon)=2,Weekend(DATADATE),
                      MonthEnd(DATADATE)))

I've been asked if we can have an option to set the dimension to display two week periods and I can't work out a way to do it. Any suggestions?

[UncleRiotous]

For clarity I realise the code above doesn't give a rolling week but I know how to do that. The issue is setting a period of two weeks rather than one.