Item type expresion to read from cell components properties

Hello:

I would like to know if it's possible to read a propertie from a cell component with an expression while creating an item type definition.

In the follownig example, I've dropped a linestyle in order to generate meshes. Doing this now I can group them and the result is exportable to an IFC. But in the process I`m lossing the line lenght.

I had thought that if I added to the group a copy of the line, I could read the lenght from there.

But when tryining to generate an expression inside the item type definition I dont know how to call those properties of the components of the group. I can only call the cell header properties.

Does anyone know how to reach those properties of the cell's components.?