Forms Data Controls :: Gridview RowCommand Event Returning Null Values?

I'm trying to retreive values entered by users in the textboxes in the footer of the gridview and insert these values into another sql table.My code is as follows :-

protected void GridView2_RowCommand(object sender, GridViewCommandEventArgs e)
{
if(e.CommandName.Equals("addnew"))
{
TextBox t1 = (TextBox)GridView2.FooterRow.FindControl("tfrm");
string frm = t1.Text;
TextBox t2 = (TextBox)GridView2.FooterRow.FindControl("tsub");
string sub = t2.Text;
string cmd = "insert into suggestions values('" + frm + "','" + sub + "','c','c')";
con.Open();
SqlCommand com = new SqlCommand(cmd,con);
int a = com.ExecuteNonQuery();
GridView2.DataBind();
con.Close();
}
}

But the strings 'frm' and 'sub' returns null values.