As you are passing hidden field value from one Page to another, you can refer below code to get value of hidden field and make Grid View textbox Enable or disable based on hidden Field value.
HTML
<div>
<script type="text/javascript">
function Enable() {
var id = document.getElementById('hfId').value;
var gridview = document.getElementById('<%=GridView1.ClientID%>');
var tr = gridview.getElementsByTagName('tr');
for (var i = 1; i < tr.length; i++) {
var tdId = tr[i].getElementsByTagName('td')[0].innerHTML;
var textBox = tr[i].getElementsByTagName('input')[0];
if (id == tdId) {
textBox.disabled = true;
} else
textBox.disabled = false;
}
}
return false;
}
</script>
<asp:GridView ID="GridView1" HeaderStyle-BackColor="#3AC0F2" HeaderStyle-ForeColor="White"
runat="server" AutoGenerateColumns="false">
<Columns>
<asp:BoundField DataField="Id" HeaderText="Id" ItemStyle-Width="30" />
<asp:BoundField DataField="Name" HeaderText="Name" ItemStyle-Width="150" />
<asp:BoundField DataField="Country" HeaderText="Country" ItemStyle-Width="150" />
<asp:TemplateField>
<ItemTemplate>
<asp:TextBox ID="txtSalary" runat="server" />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
<input type="hidden" id="hfId" value="1" />
<asp:Button Text="submit" runat="server" OnClientClick="return Enable()" />
</div>