zeevm.co.il on "[Plugin: Contact Form 7] adding a quality scale to the form"

hi, people send me files threw the contact form wich i use as an upload of images.
after choosing the file, i want to show somthing that will tell the user how large the file can be printed on.

i want to choose like :

1000 DPI = 1024X768
5000 DPI - 4000X5000

i can program but i need some instructions please.

thank you

http://wordpress.org/extend/plugins/contact-form-7/