It's possible, but there is no easy, native way to do it. You would need to do one of two things: find a third party library that does it, or write your own set of routines that open the file and parse it into meaningful chunks.
A google for "icalendar vb6" turns up a few pre-built libraries (the one I looked at was ~$300). I also found the specs for it linked from wikipedia. There should be enough information there to use msxml2.0 to load it up and begin parsing it.