Internet Explorer

I've got a page which uses gd to make an image and outputs it to the browser. The image is generated by submitting a form with the relevant data. If the form is submitted using POST, clicking File > Print in IE5.5 prints the image as if no data was submitted by the form. Using GET, the image prints as shown in the window. Is there a way round this problem as I would prefer to use POST so that others cannot see what varibles need to be passed (and exploit my work!) I think it's caused by IE saving a copy of the page and not sending the form data.