Pietlinden is right, a date table is the best and easiest. That's what we have at work. But until then, you can use a code mashup by adding to what you already have. It's not pretty, but it works! 😀

There are a million ways to do things in Report Builder, but this is just what comes to mind right now.

Also, the reason yours isn't working completely is because January 1, 2015 starts on a Thursday, so the code below just looks at the day of the week and changes it to Monday or Sunday.

This will work if you are just querying your calendar week of the year and it also looks like your "week" is Monday through Sunday. try this:

Date for starting Monday:

'----=DateAdd("d",2-DatePart("w",(DateAdd(DateInterval.WeekOfYear, Fields!WeekNumber.Value - 1, CDate("1/1/" & Today.Year.ToString())))),(DateAdd(DateInterval.WeekOfYear, Fields!WeekNumber.Value - 1, CDate("1/1/" & Today.Year.ToString()))))

Date for ending Sunday:

'----=DateAdd("d",8-DatePart("w",(DateAdd(DateInterval.WeekOfYear, Fields!WeekNumber.Value - 1, CDate("1/1/" & Today.Year.ToString())))),(DateAdd(DateInterval.WeekOfYear, Fields!WeekNumber.Value - 1, CDate("1/1/" & Today.Year.ToString()))))