HTML:

<form id="form1" runat="server">
    <div>
        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" DataKeyNames="id"
            OnRowDataBound="GridView1_OnRowDataBound">
            <Columns>
                <asp:TemplateField HeaderText="Gate1">
                    <ItemTemplate>
                        <asp:Label ID="lblGate1" runat="server" Text='<%# Eval("Gate1") %>' />
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Gate2" >
                    <ItemTemplate>
                        <asp:Label ID="lblGate2" runat="server" Text='<%# Eval("Gate2") %>' />
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Gate3">
                    <ItemTemplate>
                        <asp:Label ID="lblGate3" runat="server" Text='<%# Eval("Gate3") %>' />
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Gate4">
                    <ItemTemplate>
                        <asp:Label ID="lblGate4" runat="server" Text='<%# Eval("Gate4") %>' />
                    </ItemTemplate>
                </asp:TemplateField>
            </Columns>
        </asp:GridView>
    </div>
    </form>

C#:

protected void Page_Load(object sender, EventArgs e)
        {
            if (!this.IsPostBack)
            {
                this.PopulateGate();
            }
        }

        private void PopulateGate()
        {
            string constr = ConfigurationManager.ConnectionStrings["ConString2"].ConnectionString;
            string sqlStatment = "SELECT * from Gate";
            using (SqlConnection con = new SqlConnection(constr))
            {
                using (SqlCommand cmd = new SqlCommand(sqlStatment, con))
                {
                    using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                    {
                        DataSet ds = new DataSet();
                        da.Fill(ds);
                        this.GridView1.DataSource = ds;
                        this.GridView1.DataBind();
                    }
                }
            }
        }

        protected void GridView1_OnRowDataBound(object sender, GridViewRowEventArgs e)
        {
            if (e.Row.RowType == DataControlRowType.DataRow)
            {
                int id = Convert.ToInt32(this.GridView1.DataKeys[e.Row.RowIndex].Value);
                string constr = ConfigurationManager.ConnectionStrings["ConString2"].ConnectionString;
                string sqlStatment = "SELECT Bays from Bays Where Id = @Id";
                using (SqlConnection con = new SqlConnection(constr))
                {
                    using (SqlCommand cmd = new SqlCommand(sqlStatment, con))
                    {
                        using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                        {
                            cmd.Parameters.AddWithValue("@Id", id);
                            DataSet ds = new DataSet();
                            da.Fill(ds);
                            if (ds.Tables[0].Rows.Count > 0)
                            {
                                int bays = Convert.ToInt32(ds.Tables[0].Rows[0]["Bays"].ToString());
                                if (bays == 2)
                                {
                                    (e.Row.Cells[2].FindControl("lblGate3") as Label).Text = "NA";
                                    (e.Row.Cells[3].FindControl("lblGate4") as Label).Text = "NA";
                                }
                                if (bays == 3)
                                {
                                    (e.Row.Cells[1].FindControl("lblGate2") as Label).Text = "NA";
                                    (e.Row.Cells[2].FindControl("lblGate3") as Label).Text = "NA";
                                    (e.Row.Cells[3].FindControl("lblGate4") as Label).Text = "NA";
                                }

                                // likewise generate the code for others
                            }
                        }
                    }
                }
            }
        }

Image:

As you can see row 1 and 2 are changed. i am comparing the DataKeyValue which is Id to the Bays table column Bays