Is it possible to link any effect value to a grayscale map?

[Man Singh]

Can we use luminance of a black & white layer to define which areas should have an effect applied? For example, can we apply turbulent displace to a layer than use a precomposed fractal noise layer to define how much turbulent displace has to be applied & to which areas of the layer?

[Filip Vandueren]

In this case, you could replicate turbulent displace with a regular displacement effect that references a noise map.

You can then use a 2nd fractal noise layer to mix in patches of 50% gray: 50% = no displacement.

[Man Singh]

I used turbulent displace only as an example. I want a method where I can link intensity/slider value of any effect to luminance of a luminance map.