Setting an input from a list of optional parameters

How would you add a list to a custom component to set the parameter. I
have a list of parameters that i would like the user to choose from, to
set an input for a custom module, similar to the way one chooses input and output type for a normal custom .net module. Further more i would like to have a
second list update depending on the users first choice. Which would set a
second parameter for input. Any Ideas?