Changing the width of the modal form

Changing the width of the modal form

Hello, I am using the modal form example on the following link to create a form on my website..  http://jqueryui.com/dialog/#modal-form But the field that I have used in my form is an upload file field which requires more width than the regular modal form mentioned in the example. I wanted to know if there is a way I would be able to change the width of the form that pops up on the click of a button.