Public Class frmCheckDateTime2
 
 
    'Für die Auswahl der Zeitintervalle
    Dim dt As New DataTable
    Dim bs As New BindingSource
    Dim WithEvents dgv As New DataGridView With _
        {.Parent = Me, .DataSource = bs, .Width = 700, .Height = 300, .ReadOnly _
        = True}
 
    Dim WithEvents btncheck As New Button With _
        {.Parent = Me, .Top = 350, .Text = "check"}
 
 
    Private Sub frmCheckDateTime2_Load(sender As System.Object, _
        e As System.EventArgs) Handles MyBase.Load
 
        Me.Width = 720
        Me.Height = 400
 
        dt.Columns.Add("StartTime", GetType(String))
 
        For i As Integer = 1 To 7
            Dim wdn As String = _
                DateAndTime.WeekdayName(i, False, FirstDayOfWeek.Monday)
            dt.Columns.Add(wdn)
        Next i
        For hr As Integer = 0 To 23
            dt.Rows.Add(hr.ToString & ":00")
            dt.Rows.Add(hr.ToString & ":30")
        Next hr
 
        bs.DataSource = dt
 
        dgv.MultiSelect = True
        dgv.SelectionMode = DataGridViewSelectionMode.CellSelect
 
        Using g As Graphics = dgv.CreateGraphics
            For i As Integer = 0 To dgv.Columns.Count - 1
                With dgv.Columns(i)
                    Dim sz As SizeF = g.MeasureString(.HeaderText, dgv.Font)
                    .Width = CInt(sz.Width * 1.1)
                    .DefaultCellStyle.SelectionBackColor = Color.Yellow
                    .SortMode = DataGridViewColumnSortMode.NotSortable
                End With
            Next i
         End Using
 
         With dgv.Columns(0).DefaultCellStyle
            .SelectionBackColor = .BackColor
         End With
    End Sub
 
 
    Private Function GetWeekday(ByVal dtim As DateTime) As String
        Return dtim.ToString("dddd", Globalization.CultureInfo.CurrentCulture)
    End Function
 
 
    Private Function CheckTime(ByVal dtim As DateTime) As Boolean
 
        Dim weekday As String = GetWeekday(dtim)
        Dim colindex As Integer = dt.Columns.IndexOf(weekday)
 
        For i As Integer = 0 To dgv.Rows.Count - 1
            If dgv.Rows(i).Cells(colindex).Selected Then
                Dim parts() As String = _
                   dgv.Rows(i).Cells(0).Value.ToString.Split(":"c)
                If CInt(parts(0)) = dtim.Hour Then
                    If CInt(parts(1)) = 0 And dtim.Minute < 30 Then Return True
                    If CInt(parts(1)) = 30 And dtim.Minute >= 30 Then Return True
                End If
            End If
        Next i
        Return False
    End Function
 
 
    Private Sub btncheck_Click(sender As Object, _
        e As System.EventArgs) Handles btncheck.Click
 
        If CheckTime(Now) Then
            MsgBox("Im Intervall")
        End If
    End Sub
End Class