I guess this is what you want to achieve, though you’re trying to change a read-only parameter which to my knowledge is not possible unless it is changed on the family.
There are several threats about this:
@kulkul In the above picture, slope is the value ‘50’ right?
Hey Zak. It appears that you are trying to change a read-only value which can only be changed when you are in the edit mode of Revit. You cannot change a read only function from Dynamo. Perhaps, you can import values from Excel and change it through Dynamo.
You can find the tutorials here.
Have you tried taking it one step further?
let dynamo find which diffusers are in which zone and populate the actual zone air flow based on the summation of all the supply air flow of diffusers? Below is the question I have started… it would be great if you can share your thoughts on it.