In the Expressions tab select the Count(Product) expression and tick the 'Has Error Bars' tick box.
Click on the '+' next to that expression and select an error bar e.g. 'Error Symmetric' and make the definition =5 (or select one of the other error bars and try different definitions to get the particular effect you want).
You can add conditional logic in the definition to control when the bars appear.
On the Presentation tab you can control the width and colour of the Error bars which can make them blend in a bit more and also fiddle with the default symbol size to make then line up with the error bar ending.
Using Error bars like this on expressions for emphasis or to get reference lines on the x-axis is an old Excel chart trick.
I'm not able to upload qvw files at the moment so I hope this is enough description,
Regards,
HD
