How to add a vertical line to the scatter chart

To add a vertical line to your line or scatter chart, do the following:

   1.   Add the date with current date to your data, for example:

   2.   Add a new data series to your chart, do one of the following:

• On the Design tab, in the Data group, choose Select Data:
  
• Right-click in the chart area and choose Select Data... in the popup menu:
  

In the Select Data Source dialog box, click the Add button and in the Edit Series dialog box, type:

• In the Series X values box - the cell with current date ($C$1)
• In the Series Y values box - constant value (100):

   3.   Select new date series, under Chart Tools, on the Layout tab, in the Analysis group, choose the Error Bars and then select More Error Bars Options...:

In the Format Error Bars dialog box, type parameters of the vertical line:

You can then make any other adjustments to get the expected look.