How to store an array to a hidden fld

[wxdqz]

I have developed a web page which allows the user to select
numerous items from a combo - box. Each selection is stored in an array. I allow the user then to review the selected items - adding or deleting as needed until all the selections are correct. All the items are elements of an array.
When the form submit button is selected I am trying to concatenate all the array elements to one string and assign the string to a hidden field which I have already defined on the form.
I have tried this and tried this and I cannot tell why it is not working ...
the hidden field always appears blank

I am using the following function to concatenate the array elements and assign the resulting string to the hidden field named selected_forms:

function arrange(){
var xobj= 1;
var formStr;

for(xobj>0;xobj<IDSelect;xobj++){
if(formsel[xobj]!= ""){
formStr=formStr+formsel[xobj];
}
}
document.CopyCenter.selected_forms.value="Line="+formStr;
}

This doesn't work - an ASP script which is used to process the form - data . reports this field as blank or that the data is undefined ????????
Help please - Thank you .