How can I DVH evaluate a PTV1-PTV2 structure without creating a new one?

[avalgoma]

Good morning and thanks in advance.

I have a plan with PTV1 and PTV2 structures, and I need to calculate GetVolumeAtDose(PTV1-PTV2,...). I know I can create a new PTV1-PTV2 structure to this goal, but I don't want to modificate the plan because I want to use a read-only script.

Is it possible?

Regards,

-- Agus