slope change

I am almost positive there is an indicator that will sound or indicate somehow when slope has changed from positive to negative or vice versa. Could someone please direct me to it? Thank you

Here is one from The Kolachi Method of Trading,

http://www.forexfactory.com/forexfor...19&postcount=5

shucks....
That's not it.

The 'Momentum' indicator in MT4 does measure slope but it's normalized (to 0-100 range, I think).