You will tend to get better responses if you post small, relevant portions of your code and are explicit about exactly what happens when 'nothing works'. Looks like you were lucky this time ... duff and davidrw have provided a good start to what you need. :)

You might also consider reading How do I post a question effectively?.

I think you're on the right track if you consider what characters can occur in a legal filename and build a regular expression that will filter out characters that fall outside that set. Write some code and post it here if you still need more help. :)