Passing value to Overlay

Hi,

I have requirement to have one colume in datatable as img button. When i click on that it will open a overlay which have a textbox to edit the data from data table.

the following is the img to open the overlay

<wec:graphicImage id="btn" rendered="true" value="#{wec:themeUrlOf('images/btn.png')}" onclick="#{wec:openOverlay('overlay','btn'')}"/>

I have no idea how to pass the value or object ref from the datatable to display in the overlay,then save it.I have tired to search in the help but can not find it.

Can you advise

Thank you in advance,

Noppong