Resetting drop-downlists in input-fields for texts

I'm developing a traning page for basic math. The answers are entered by the user in simple text input fields and the same page is returned (after having been processed by php) to the user with indications of correctness or error on each answer. If the AutoComplete feature is turned on a droplist with previous entries are displayed in the answer fields, even if new exercises are generated. This is quite distracting. Is there any way I can block this feature from my php-code, even if it is turned on in the users browser? Tor