changing a variable according to the input in a checkbox

How would I be able to change a variable from the input in a checkbox? I need to write an sms script, that would be able to sms to three different providers, and I only want the use to type in the phone number. Thus, if he types in 083xxxxxxxxxx, it should goto provider 1, if he types in 082xxxxxxxxxx, it should goto provider 2, and if he types in 084xxxxxxxxxx, it should goto provider 3. I have a simple mail script, with $phone for the phone number variable, and this is the one that needs to change. Rudi Ahlers UNIX Specialist and Web Developer Bonzai Web Design - http://www.bonzai.org.za Cell: 082 926 1689