Find path progress at specific point

Hi

Thanks to Adobe for adding path access through expressions, that's awesome.

With this expression I can set anothers layers position to be exactly half way on a path.

var pathLayer = thisComp.layer("Shape Layer 1");

var progress = 0.5;

var pathToTrace = pathLayer("ADBE Root Vectors Group")(1)("ADBE Vectors Group")(1)("ADBE Vector Shape");

pathLayer.toComp(pathToTrace.pointOnPath(progress));

My question is; is there a way to get the progress for specific Point (anchor/vertex) on the path. Say the path is made out of five points, can I somehow get the exact progress for the second point?

Did that make sense? If not please ask.

Thanks,

Jakob