For getting total you have to use for each loop for getting value of amount from label.
use this code-
protected void GetTotal_Click(object sender, EventArgs e)
int Rowtot = 0;
foreach (GridViewRow r in GridView2.Rows)
Label lblTot= (Label)r.FindControl("lblEAmount");
if (lblTot != null)
Rowtot = Rowtot + Convert.ToInt32(lblTot.Text);
txtTotal.Text = Rowtot.ToString();
TRY THIS CODE AND LET ME KNOW.