You can add Tooltip from the Pivot >> Data Groupings >> Values >> Action tab, Tooltip field
You can explore some of the online examples, for example:  Scale Breaks

Hopefully this helps.

Best Regards,
Nevron Support Team

I don'tt want a drill down. i just need to show total (sum) sub value in the tool tip

Hello Reynaldo,
You can have Tooltips on mouse-over showing the data point value or something else.
To add a Tooltip, you need to use an expression in the Pivot >> Data Groupings >> Values >> Action tab, Tooltip field

For example, if the Value for your bar series (in the Pivot >> Data Groupings >> Values >> General >> Data) has an expression like: =SUM(Fields!Value), you need to use the same expression in the Action tab >> Tooltip

You can have more complex expressions for showing Tooltips. For example, the following topic explains how you can use parameters interactive drill-down chart and also have Tooltips based on these parameters: http://support.nevron.com/KB/a203/create-interactive-drill-down-chart-in-sharepoint.aspx

Best Regards,
Nevron Support Team

Hello

I would like to use the mouse-over to show the value of the bar in a bar graph. Is this possible?