[Discuss-gnuradio] creating custom block with variable number of inputs/outputs

Hello, 

I am trying to create a custom block that can take in a variable number of inputs and outputs based on what the user enters. I have tried looking at the source code of the "Add" block to figure out how to do this, but it is still not clear where and what I should modify to accomplish this. Any help would be appreciated. 

Thanks, 

Vincent