How To Add Client Script To A Pushbutton In Datagrid

I am using a datagrid in my asp.net web app to show a user list. I put a
pushbutton (could be linkbutton as well) for each row in the grid. I would
like to have a javascript function linked to each button, so when user clicks
the button, another pupup window shows up to show an image of the selected
user in the list. I am looking for a way to add client side javascript
function to each button and passing the each user's key to the function.