Equation in Welded Parts List

Good evening

Is it possible to put an equation in the value of a welded part item?

Example:  Dish Ep: "D1@Boss.-Extru.1@Pièce1.SLDPRT" + 5

I have the impression that it is not possible...

Thank you in advance

Hello 

Which version are you on? Can you post a part file so we can try?

We are in 2018

Hello

No ideas?

Do you want the coin to be larger via this equation or just want it to be the value?

Yes, it is longer than 5 mm

Why not put this equation in the extrusion sketch1.

Thank you, it's to avoid that!

Why do you want to avoid this?