How to compute the numeric values of DataGridView's Column [Field] and result value to be in next row?

C#:
 In my application program, i had placed a DataGridView for tabular format. Here what i
need is to calculate the numeric values of a column which is in datagridview and the
result should be in the next row of that column and/or some other textbox named as resulttb.
  For Example,[from the below figure] i need to calculate the total sum of the numeric
Field"Execution" like (15+25+2000+500000+10 = 502050)& "Sup_Execution" like
(2+2+50000+100000+100=150104) these total results should be placed in followed row of that
field and also in the resulttb textbox control.




And also i needs to calculate "Total"field(hidden) that the value get from the fields
(Execution) * (Sup_Execution) of row wise.