Dynamic file path in fileupload element

Hi Friends,

I know the usage of filupload element. It allows to pick the file and upload the contents.

But my requirement is, I want to upload a file whose path will be calculated dynamically. e.g. I will ask user to enter some string and based upon that string I would like to choose a file from a predefined folder. I mean I want to supply the filepath dynamically.

Please suggest the way to choose file dynamically.

Thanks

Krishan