Control Z Position of multiple Layers with one controller

[Robert Müller]

Hey Marcel, this should do what you are looking for:

fac=thisComp.layer("ctrl").effect("factor")(1) //slider on a Null layer
x=value[0];
y=value[1];
rdmMin=-100; //Min random value
rdmMax=100; //Max random value
rdmSeed=123456 //random seed
seedRandom(rdmSeed, timeless = true); //timeless is true, so the value doesnt update every frame
rdmVal=random(rdmMin, rdmMax);
z=rdmVal*fac;
[x,y,z]
Now when you animate your slider on the control layer from 0 to 1 the layers will start moving up to their random z position. You can increase this if you go beyond 1.
If this is not random enough you could always factor each layers index into the seed, so you would have a individual seed for every layer. If you want a more natural random distribution you could use “gaussRandom()” instead of “random()”

[Marcel Schobel]

Thank you Sir !
this does the trick. I am pretty solid at After Effects in all areas EXCEPT for Expressions. I wish i could wrap my head around that. I can even understand/interpret your expression (kind of) BUT i just cannot come up with one myself … i will try to learn in the next couple of weeks …been neglecting expressions for way too long.
thanks again for your time and kindness
regards