Naturel ventilation rate of flow variable, linked with shading

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Hello, I'm working on DesignBuilder and would like to include in my simulation the variability of the rate of flow for the natural ventilation due to the shading system. Natural ventilation flow will physically decrease when the shading is partially or fully closed, but DesignBuilder doesn't link those data and consider the natural ventilation as if the shading system didn't exist. I wonder how to include this data by using the Script EMS. But I've never used the script tool although I do have the licence. If anyone knows how to create this script or has any idea on how to solve this problem, I'm very interested! Thank you very much, I hope my question is clear. If it isn't, please ask me more information.