Detect when redirected standard input is needed in a Windows form calling an external process

Question

This is what I would like to do: a windows form app calls a console script to do a subtask. I might redirect output to a textbox or something. But I would like to pass input to the console script, when needed, through say a custom popup window which has a textbox + button that invokes a "browse for file/folder" dialog. This can be done for passing initial command line arguments but how about redirected standard input? Is there a method to detect when a console program prompts for standard input? --so that I can invoke my code to launch a popup and pass that data back to the standard input of the script?