define a operation to a straight line

Hi

In the example below the trend line is down (negative or decrease) and I want to know as to do indicate in system, for example, IF.......to do for example a open position

The expression to generated this tendency curve is:

var sma = Indicators.LinearRegressionForecast(source,15);

and now, continue with a conditional question.......

If...........

make something....open position...

Please, can you suggest me the information to solve this?

tks

Eli