Classic ASP validate form input File type

I need to know how to check if is a value is in the input field of type file in classic ASP. The input field name and id is file, and type is file. The form type is multipart/form-data and name form1.

I am using Upload.asp object by Jacob Gilley to handle my uploading. If the user submits without selecting a file to upload; the site errors out. The user should have the option to submit with or without a file. I need to validate on the server side.

I try
len(Uploader.form("file"))) > 3

Thanks for any help
David Pearson