Javascript code cached in browser

I have a below inline Javascript code in my aspx page of asp.net web application.

 function Confirm_Popup(dealid) {
 var bVal
 bVal = confirm("Are you sure you want to assign the same deal again?");
 if (!bVal)
    window.location.href = "page.aspx?id=" + id;
else
    window.location.href = "page1.aspx?id=" + id; 
}

I am calling the code from code behind file like below.

ScriptManager.RegisterStartupScript(Me.Page, Me.GetType(), "showalert", "Confirm_Popup('" & Id & "');", True)

Step 1: Open the the page link for the first time.

Step 2: Open the same link again in new tab.

Issue is I am getting confirm Pop up in Step 1 but Step 2 is not giving pop up. Requirement is to display pop up in step 1&2. It seems like code is cached by browser.

Kindly help.