script or extension for chrome or firefox -- 2

we need something will allow us to be able to send messages to all contact names includes "266"
whatsapp allows only 5 message on mobile but web.whatsapp.com here we can send manually, we need you to develop something so we can send to all matching contacts

something that will work on firefox or chrome
it will enable us to send message to all matching contacts ,
we will enter once and message will be sent to all matching contacts
for example contact names starts with 266 or there is 266 in the names