This is all that you need to do to access a TextBox that is in a GridView from JavaScript:
<form id="form1" runat="server">
<asp:GridView ID="GridView1" AutoGenerateColumns="False" ShowHeader="True" runat="server">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:TextBox ID="gridTextBox" onchange="gridTextBoxOnChange(this);" runat="server"></asp:TextBox>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
</form>
<script type="text/javascript">
<!--
function gridTextBoxOnChange(elementRef)
{
alert('TextBox: ' + elementRef.id + ' Value: ' + elementRef.value);
}
// -->
</script>
NC...