You are probably better off using the worksheet for this.

A straight line needs only two points. Suppose the x values are in A
and the Y values in B starting with A2. Then, the formula
=IF((B3-B2)/(A3-A2)C1,"Watch it!","Normal")
gives you what you want. The threshold for the slope is in C1.

You add a conditional format to the cell containing this formula so
that the 'Watch it' is in red and the 'Normal' in green.

You could also add a textbox in the chart and link it to this cell.
That way the state is also in the chart. To do so, click the chart,
enter the equal key then click on the cell containing the formula.

--
Regards,

Tushar Mehta
www.tushar-mehta.com
Excel, PowerPoint, and VBA add-ins, tutorials
Custom MS Office productivity solutions

In article ,
says...
Hi everyone I have an interesting one..

I have been wondering for a while if it is possible to have a trigger or a
message if a chart is created or updated to show a line chart with a line
taking a certin gradient indicating an increase which must be monitored.

Thanks for your help.

Rob