Don't use DataAdd in VB.NET.
vb.net Code:
  1. Dim myDate As Date = Date.Today
  2.  
  3. 'Add a week.
  4. myDate = myDate.AddDays(7)
  5.  
  6. 'Add a month.
  7. myDate = myDate.AddMonths(1)
  8.  
  9. If (myDate.Month = 12 AndAlso myDate.Day >= 15) OrElse _
  10.    (myDate.Month = 1 AndAlso myDate.Day <= 5) Then
  11.     myDate = myDate.AddDays(21)
  12. End If
You could use Date literals at the end there but the way I've done it will work for any year. You can also use variables for the days of December and January if they will vary.