How can I pass a CDT to an interface?...

On the form that is using that interface create an activity class variable on the input tab. Create the ac variable with the correct cdt type and value that you would like to use in the interface. Then create an input on the interface with a type of 'Any Type'.

On the form that is using that interface create an activity class variable on the input tab. Create the ac variable with the correct cdt type and value that you would like to use in the interface. Then create an input on the interface with a type of 'Any Type'.