multiple file uploads on same form

Hello,

I have a form with 5 file upload spaces (input type = file) and I would like the first one to be available only (the rest disabled) and have the others become available as they are filled in. For example, if the user clicks 'browse' and adds a file to the first box, the second will become available, etc. etc. Following that, I would like it to determine how many of the fields have been used (count the number of "enabled" fields?) and report that back in a variable.

Is this action possible (prefer in VBScript) ... if anyone knows where to find a working example, please offer directions or any other insight.

Thanks.