Use the SelectLevel property to specify the area being highlighted when a date is selected. For instance, if you click a date in the first level ( in the chart's header ), the chart displays the selected date accordingly to the selected level. Use the SelectDate property to select or unselect a new date, or to find if a specified date is selected or not. Use the LevelFromPoint property to retrieve the index of the level from the cursor. You can select multiple dates keeping the CTRL key and clicking a new date. The MarkSelectDateColor property specifies the color being used to highlight the selected dates. If the MarkSelectDateColor property is identical with the BackColor property of the Chart object, the selected dates are not shown. 

In the following screen shot the red lines marks the selected dates ( June 20 and June 28, as the user clicks the June 20, 28 dates in the second level ( index 1 ) where the days are displayed ):

In the following screen shot the red lines marks the selected week ( June 19 to June 26, as the user clicks the June 19, `05 week in the first level ( index 0 ) where weeks are displayed ):