Arc between two arcs

[Paula8 (Paula)]

Hello, I need to create an arc in between to other arcs and I don´t know how to do it.It needs to do like this.

[Cumberland]

Curve/Spline/Tween Curve.

Arc between.gh (2.9 KB)

[leopoldomonzani]

[Volker_Rakow]

If the upper curve is actually separate curves, join them first with Join Curves. Then put the joined uppper curve with the bottom curve into a Tween Curve, reparamterizing their inputs.