Ok I have got it so you click on one and the file.txt opens...but I want it now so you click on the next object in the listbox and it gets rid of file.txt and opens up file2.txt in the label
and another thing...

It will only add one line in the .txt file...say the file looks like this

Testing
Hello This Is A Test
This Should Work
It will only put "This Should Work" down no matter what I do, unless I delete it and move "Hello This Is A Test" down a few lines