Customize the cell value of the WinForms MonthCalendar.

//Handles this event to provide custom formatting for calendar cells.
this.monthCalendarAdv1.DateCellQueryInfo += new Syncfusion.Windows.Forms.Tools.DateCellQueryInfoEventHandler(monthCalendarAdv1_DateCellQueryInfo);
void monthCalendarAdv1_DateCellQueryInfo(object sender, Syncfusion.Windows.Forms.Tools.DateCellQueryInfoEventArgs e)
{
    if (this.monthCalendarAdv1.Value.Date == DateTime.Today)
    {
        //Disables the highlight color of the selected date value.
        e.EnableHighlightColor = false;
    }
    if (e.RowIndex == 3 || e.RowIndex == 4)
    {
        //Customizes the particular cell value.
        e.Style.BackColor = Color.Red;
        e.Style.TextColor = Color.White;
    }
}

'Handles this event to provide custom formatting for calendar cells.
AddHandler monthCalendarAdv1.DateCellQueryInfo, AddressOf monthCalendarAdv1_DateCellQueryInfo
Private Sub monthCalendarAdv1_DateCellQueryInfo(ByVal sender As Object, ByVal e As Syncfusion.Windows.Forms.Tools.DateCellQueryInfoEventArgs)
    If Me.monthCalendarAdv1.Value.Date = DateTime.Today Then
        'Disables the highlight color of the selected date value.
        e.EnableHighlightColor = False
    End If
    If e.RowIndex = 3 OrElse e.RowIndex = 4 Then
        'Customizes the particular cell value.
         e.Style.BackColor = Color.Red
         e.Style.TextColor = Color.White
    End If
End Sub