getting file size before upload

Hi there, I know it is a often asked question, but after googling for about 2hours and trying out some wired examples I am still not any closer to a solution. So I was hoping to find expert advice here. I want to save the user the hastle of uploading a 2MB file and waiting for a long time for an error message that the file is to big. Is there any usefull workaround in warning the user that he is about to upload a 2MB file and only smaller files are supported? I tried around with megaupload: http://sourceforge.net/projects/megaupload to get a progress bar and to get the file size prior to upload, but that somehow does not work the way I want it to. Is there an easier solution without perl,just with PHP or/and JS? Thank you for any hint on this, Merlin