Once you have two DateTimes and the comparand, the test is pretty simple.
Does this help?

public static bool DateBetween(DateTime start, DateTime end, DateTime date)
 {
  if ( date >= start && date <= end )
   return true;
  return false;
 }

Geoffrey,
I defined a TimeRange type that is useful to check to see if a DateTime
falls within a certain Time Range (for example between 8AM & 5PM). See:

http://groups-beta.google.com/group/microsoft.public.dotnet.languages.vb/msg/809
aa87555043055

It would not be that hard to utilize this type in a larger type that
included one or more Days of Week. Something Like:

Public Structure DayRange

   Private ReadOnly m_time As TimeRange
   Private ReadOnly m_days() As DayOfWeek

   Public Sub New(ByVal time As TimeRange, ByVal ParamArray days() As
DayOfWeek)
       m_time = time
       m_days = days
   End Sub

   Public Function Contains(ByVal value As DateTime) As Boolean
       Dim index As Integer = Array.IndexOf(m_days, value.DayOfWeek)
       Return index <> -1 AndAlso m_time.Contains(value)
   End Function

End Structure

       Dim range As New DayRange(New TimeRange(#8:00:00 AM#, #5:00:00 PM#),
DayOfWeek.Monday)
       Dim value As DateTime
       value = #3/29/2005 10:00:00 AM#
       Debug.WriteLine(range.Contains(value), value.ToString())

       value = #3/28/2005 10:00:00 AM#
       Debug.WriteLine(range.Contains(value), value.ToString())

The above DayRange assumes you want to check a specific Date & Time value,
such as DateTime.Now, it should be easy to modify to check a Day of week &
Time value.

Hope this helps
Jay