jQuery – Detecting if a file has been selected in the file input [duplicate]

Possible Duplicate:
jQuery: get the file name selected from <input type=“file” />

I have a standard file input box

<input type="file" name="imafile">

I also have a bit of text down the page like so

<span class="filename">Nothing selected</span>

I was wondering if it is possible to have the text update with the name of the file selected in the file input box?

Cheers,