[Zope] verify whether html <input type=file... is empty

[Andrei Belitski]

Hi!
Don't know if it is really a zope question, but I have a problem,
verifying if e.g. input
<INPUT TYPE="file" NAME="image_1" SIZE="50">
is empty or not using
    <dtml-unless " REQUEST[ 'image_1']=='' ">
       <dtml-call "manage_addImage( id=imageId, file=REQUEST[ image_1],
REQUEST=REQUEST )">
    </dtml-unless>
well, I think the <input type=file... is not a string, but what I want
to test is if the user put in the filename and not whether the really
existing file is empty, so how could aI do it?

I would appreciate any hints
Thank you in advance
Andrey