You will need to use the <a href="http://addons.oscommerce.com/info/4703" target="_blank">Zone Shipping by State Add-On</a>.
You install the Add-On similar to our <a href="http://www.inmotionhosting.com/support/edu/oscommerce/config-tax-payment-shipping/zone-rate-shipping" target="_blank">Setting Up Zone Rate Shipping in osCommerce article</a>.
The plugin developer states "This contribution is specifically for shipping within the United States and the only language file included is for English. It should be relatively easy to modify for use in other countries." They also have a threat you can ask questions on below.