How do you show a field if a file has been uploaded?

How do you show a field if a file has been uploaded?

Here's what I'd like to do:
When a user uploads a file another file upload field appears.
To do this I've created a maximum of 6 file update fields:
Documentation
Additional_File_1
Additional_File_2
Addition.....3
....4
....5

My current scripts...

Form Action:
On Add/On Edit - On Load
hide Additional_File_1;
hide Additional_File_2;
hide Additional_File_3;
hide Additional_File_4;
hide Additional_File_5;

Field Actions:
Documentation - On User Input  
show Additional_File_1;

Additional_File_1 - On User Input
show Additional_File_2;

(continue until Additional_File_4 shows 5)

This works but the problem is that the user input is the only thing that shows the files. In editing, only the Documentation field is shown.

I spent a lot of time implementing an IF function but I don't think I have the right syntax. This IF function normally works for other fields but I don't think it applies to the File Upload field:

if (count(Feed[Documentation == input.Documentation]) > 0)
{
    show Additional_File_1;
}
else
{
    hide Additional_File_1;
}

if (count(Feed[Additional_File_1 == input.Additional_File_1]) > 0)
{
    show Additional_File_1;
    show Additional_File_2;
}
else
{
    hide Additional_File_1;
    hide Additional_File_2;
}


I suspect that the COUNT function does work for File Upload fields. If this is the case, what should my script be to indicate that if Documentation has a file, show Additional File 1, if Additional File 1 has a file, show Additional File 1 AND show Additional File 2?

Brent