How to use code to define parameters in an API Call

Hi, I’m new to building plugins and still learning. Could anyone share how I could run the code (which returns the milliseconds since 1st Jan 1970) and input this data into a parameter on an api call in the plugin builder? Would I need to create an action that performs this and then tell the user to input this action into another action that makes the API call, or is there some way I can do this in one step so that the user doesn’t even see the timestamp step?

Essentially on every parameter call I want this timestamp to be included and its much simpler for the User if they don’t have to worry about this step.