Combinations of a String

This is in response to a question on posted on the Programming Q & A section. It takes a string and fills a listbox with all combinations of the letters in the string (could be adapted to use a dynamic array, too, the listbox was better for demonstration purposes). This program use recursion to get it's results and may be a good example for someone learning the concept to step through. Warning: The number of combinations goes up exponentially! more than 8 characters will work but really bog down your PC!