Why don't you get the current week this way:
Dim week as Integer = Convert.ToInt32(Math.Ceiling(Convert.ToDouble(DateTime.Now.DayOfYear) / 7)
Dim CntWeek as String = string.Format("{0} - {1}", week, DateTime.Now.Year)
EDIT =============
I would create an extension method like so (this is C#, but shouldbe easy to convert to VB). Then you could use it for any date you wish instead of just today's date:
public static int WeekOfYear(this DateTime date)
{
int week = (int)Math.Ceiling((double)date.DayOfYear / 7);
return week;
}