JQuery :: Create Querystring With Parameters In Aspx Using Vars?

I'm trying to create a querystring in my aspx page. I need to pass in 2 variables as parameters. The end goal is something like this:

Popup.aspx?paramOne={0}&paramTwo={1}

I have a function that needs this string.

$("#<%=FindButton.ClientID %>").click(function() {
var paramOne = $("#<%=ParamOneDDL.ClientID %>").eq(0).val();
var paramTwo = $("#<%=ParamTwoDDL.ClientID %>").eq(0).val();
var queryString ='<%= string.Format(Constants.MyPopupQuerystring, paramOne,

[Code]....

That doesn't work. It doesn't recognise paramOne and paramTwo with that syntax, so i tried to use the DDL.SelectedValue directly and that doesn't work either as it doesn't find a value for some reason. I can manually set up the string as follows: queryString = "MyPopup.aspx?paramOne=" + paramOne + "&paramTwo=" + paramTwo);

which works but is not good coding practice as I don't want to hard code stuff.
What is the correct notation to do this?