Plugin for getting attribute values from a grid ?

Hi All,

I have a requirement like , on product form I have placed a product line item grid in that form I have added a custom column cost.Product and Productlineitem has 1:N relationship.

Now I need to get the cost column value from the productlineitems records associated with the product and add the total cost and place it on product form.

For this I need some code in plugin how to get the values from the productlineitems records.

Please help me..