This function will figure out if the given date lands on a weekend.

    Public Shared Function IsWeekend(ByVal dateOfInterest As DateTime) As Boolean
        Dim d, m, y, w As Integer
        d = dateOfInterest.Day
        m = dateOfInterest.Month
        y = dateOfInterest.Year


        If m = 1 Or m = 2 Then
            m += 12
            y -= 1
        End If


        w = CInt((d + 2 * m + 3 * (m + 1) / 5 + y + y / 4 - y / 100 + y / 400) Mod 7)
        If w <> 6 And w <> 7 Then
            Return False
        Else
            Return True
        End If
    End Function

Another function to do the weekend check could be this:

    Private Const ERR_INVALID_DATE = 20000
    Private Const ERR_INVALID_DATE_MSG = "Date Required"

    Public Function IsWeekend(ByVal DateValue As Object) As Boolean

        Dim dDateValue As Date

        If Not IsDate(DateValue) Then
            Err.Raise(ERR_INVALID_DATE, ERR_INVALID_DATE_MSG)
            Exit Function
        End If

        dDateValue = CDate(DateValue)
        IsWeekend = (Weekday(dDateValue) Mod 6 = 1)

    End Function