If I use the following:
function openFSCUploadDialog()
{
    var diaOptions = SP.UI.$create_DialogOptions();
    diaOptions.url = "<server>/mySite/_layouts/Upload.aspx?List={E2489E65-BE6T-4569-BE36-FCE8D47DG8EB}&IsDlg=1&ReqID=1";
    diaOptions.width = 700;
    diaOptions.height = 310;
    diaOptions.title = "Trying to Pass the Value in the Dialog URL";
    diaOptions.dialogReturnValueCallback = Function.createDelegate(null, CloseCallBack);
    SP.UI.ModalDialog.showModalDialog(diaOptions);
}
to open a dialog of the upload.aspx for the site collection. I am trying to use javascript/jquery and read the value from a query string that I have passed in the above dialog.url. I am unsure of how to access the value in the code behind of the upload.aspx using javascript / jquery.
I would really appreciate any context / help on this.
EDIT: yes sorry I would like to access the value in the something like the $(document).ready of the form.
 
    