Jscript help

[yellayi@xxxx]

I am trying to calculate the sum of daily volume in a descending 
order and I get a run time error with the following code.

EnableScript("jscript");
<%
Vol = VBArray( AFL( "Volume" ) ).toArray();

// perform the loop that calculates Sum of Volume

k = Vol.length;
Sumvol = 0;

for( i = 0; i < k ; i++ )
{
Sumvol = Sumvol + Vol[ k - i ];
}

AFL.Var("Sumvol") = Sumvol;
%>

Filter = C>0;
NumColumns=2;
Column0=Close;
Column1 = Sumvol;

If I change the expression in the for loop to 
Sumvol = Sumvol + Vol[ i ];

it works. However, that is not what I want. Any help is appreciated.

Also the following for loop gives an error , I don't know why?
for( i = k; i > k -5 ; i--) -- doesn't seem like i--


thanks

mohan