Multiplication operation of columns in datagrid ..?

Gi Guys,
Please solve my problem ,
these things are not working ..............
 

select amt as AMOUNT,Quantity as Quantity ,(amt*Quantity) as Total from "TABLE NAME"

try this code

DataTable dt = new DataTable();
DataColumn column4;
column4 = new DataColumn();
column4.ColumnName = "Column3";
column4.Caption = "Column3";
column4.Expression = "Column1*Column2";
dt.Columns.Add(column3);

int myTotal = int.Parse(dataGridView1(0, 0).Value) * int.Parse(dataGridView1(0, 1).Value);
 
dataGridView1(0,2).Value = myTotal.ToString();
 
dataGridView1.RefreshEdit();
 
 
my syntax might be off.  I dont mess with dataGridView much.  If the above doesn't work try dataGridView1.Rows[0].Cells[0].Value.   Also, remember that the rows and columns start at 0 and not 1