NX Routing Space Reservation cannot be parametrically driven

When creating Space Reservation stock in NX Routing applications it is possible to select an existing expression to control the size of the space reservation. 

Why is the space reservation not updating when the expression is subsequently changed?

When creating the space reservation the dialog allows the selection of a Formula to control the size

This presents the dialog and allows the selection of an existing expression.

The dialog will then display the value as linked to a formula/expression and the space reservation can be created

However this is misleading as the link has not been created to the expression, only the value has been used.

If the expression selected for the formula is subsequently edited the Space reservation will not update accordingly

This is working as designed. The ability to link routing stock or space reservation to expressions has intentionally been prevented. 

Routing stock or space reservation are connected together by constraints and they are always in some assembly context. Adding expressions to stock/space reservation, can add additional dependencies including inter part dependencies. This will make the update process very complex and fragile. That is why Routing has not added any expressions to stock/space reservation.

Enhancement request ER 10137110 is currently in review for adding the ability to use expressions for Stock and Space Reservation.