Simple javascript question

I'm sure this is pretty basic stuff for the people on this board, but I'm just learning javascript so I'm struggling the like the said little lurker I am.

I have an assignment due tomorrow that requires me to write a page that requests the first and last numbers of a sequence from the user and then takes those two numbers and every number in between and displays a table with the numbers and their squares and cubes.

I really thought the script I had written would get it done but after the user enters the second number nothing happens and it just ignores the loop I wrote in. If anyone could tell me what is wrong with my script (posted below) or a different way to do it I would be grateful. I would like to avoid using functions for now as I am still a newb and am not particularly fond of them though I know I will be needing to use them alot at some point. Any help would be great anon!

<script language="Javascript" type="text/javascript">
        <!-- Hide script from old browsers
       
        document.write('<center><table width="50%" border="1">');
        document.write('<tr align="center"><td>' + "Numbers" + '<\/td><td>' + "Square" + '<\/td><td>' + "Cube" + '<\/td><\/tr>');
       
        ans = prompt("Enter the first number of the sequence.","")
       
       
       
        try
            {
            if (!ans || isNaN(ans))
               {                  
                throw new Error('That is not a number.')
               }
        ans2 = prompt("Enter the last number in the sequence.","")
            if (!ans2 || isNaN(ans2))
               {                  
                throw new Error('That is not a number. Hit F5 and re-enter')
               }
            }

        catch(errMsg)
            {
            alert(errMsg.message)
            }
        finally     
            {
                for(i = ans; i > ans2; i++)   
                {
                document.write('<tr align="center"><td>' + i + '<\/td><td>' + i*i + '<\/td><td>' + i*i*i + '<\/td><\/tr>');
                }
            }   
       
       
            // End hiding script from old browsers -->
    </script>    

the html comments hide the script from older browsers that don't understand it,
Anyone using a browser that hasn't been updated in 15 years deserves to have things break.

it's part of the class and I have to put it in there so tell it to my professor
Your professor is full of shit.