Dynamo stating parameter is read only

The following code is being used on a project in which a curtain consisting of adaptive panels is placed upon a conceptual mass.

One of the parameters used to define the change in these panels is its NCP value which I can change when editing the mass across any given panel, this is the aim of the shown code, however, in the final stage where it is to set the NCP parameter, it states that it is read-only. Is there any way to solve this issue

Thanks, Rian