Chocolate bars are going interactive.

In a Willy Wonka type competition, confectionery maker Cadbury's is planning to hide codes inside the wrappers of millions of chocolate bars.

By sending a mobile phone text message containing the code to Cadbury's, chocolate lovers can win prizes such as DVD players and widescreen TVs.

The first chocolate bars containing the competition codes will be on shelves in mid-August.

Mobile munching

In the biggest trial yet of wireless advertising, confectionery giant Cadbury's will soon kick off a text message competition involving up to 65 million chocolate bars.

Printed inside the wrappers of the bars will be a code that can be sent back to a given phone number in an SMS message to see if it wins a prize. Anyone sending a message will find out instantly if they have won a prize.

The codes will be hidden inside the wrappers of any one of ten of Cadbury's leading chocolate bars including Crunchie, Time Out, Dairy Milk, Caramel, Boost, Wispa, Giant Buttons, Whole Nut, Fruit and Nut and Double Decker.

The prizes on offer include 100 chances to win �5,000 cash as well as Playstation 2s, Palm and Psion handheld computers and compilation CDs. Television adverts will be used to drum up interest in the competition.

Cadbury's is expecting a big response to the competition because young people are both fans of chocolate and text messaging. Around 75% of 15-29 year-olds now possess a mobile phone.

The Short Message System (SMS) is becoming very popular as a promotion tool for many companies. Already the text messages have been used to let visitors to shopping malls know about special offers. Soon many mobile phone users will be getting discounts on their phone bills because they have agreed to accept advertising messages on their mobile.

Mobile messaging company Flytxt is providing technical help with the promotion.