newbie question

Question

i have a button that will extract 2 columns from a selected row (the button is not a buttonfield btw, its a standalone asp button).

 the first column was easy as the datatypes were string. the second one is a little tricky (for me that is) as im trying to extract the "unit price" from the selectedrow (gridview1.selectedrow.cells[5]) in my case. im using a label that will display the cumulative unit price from all the selected rows

heres a code that i was trying but as obvious, it has problems with datatypes.


        int invoicetotal;
        int unitprice;

        unitprice = GridView1.SelectedRow.Cells[5];

        invoicetotal = invoicetotal + unitprice;

        Label3.Text = invoicetotal;


what i want is that every time  i click on the button, the label will display the total amount of the prices that were selected.

thanks.