Extracting Numbers From Alphanumeric Strings (strip Numbers?)

I import data from another program in order to evaluate it. Unfortunately, one of the fields I need contains copyright data, however, it has been very inconsistently entered into the database. For example, sometimes the data appears "c1999." or "-1999" or "" or "[1999]" or even "19?" and also sometimes "1999, 1990" and many other variations on that. I discovered the link in the excel help file about extracting numbers from alphanumeric strings, but my situation is still too variable for it to apply; that file didn't take into account that alphanumeric strings don't always lump numbers and letters together. I was able to correct a few things, but my command of excel isn't knowledgeable enough to really come up with something effective.

Some ideas I had that I don't know how to implement: is there a way to strip non-numerical characters from an alphanumeric string? (I've been doing some find/replaces to get rid of some of it, but that is obviously not very efficient when I have to repeat this process daily.) Perhaps then I could just detect the first 4 numbers of the string somehow. However, that doesn't solve the problem of when a wild card is used as in "199?" or "20?" etc.

Bottom line, I just need to grab the first four numbers that appear in the string (but NOT additional numbers that occur after a wild card or a space if the year was not completed in 4 numbers; in that case I'd just be happy with a null value).

I've been doing this with a formula so far. My only experience with macros has been in simply recording them, not actually writing them, but I'll give anything a try.