Show progress bar with seam s:fileUpload

[bajrang]

I want to show progress bar to display what percentage of file is uploaded. I am using rich:progressBar with seam fileupload tag.

<rich:progressBar id="progrs" interval="1000" enabled="true" value="#{managedBean.currentValue}" minValue="1" maxValue="100" label="#{managedBean.currentValue} %"/>
<s:fileUpload ......./>

I am having problem, how can I get the current size of uploaded file.
After having this value, I can calculate percentage.

Thanks in adv.