Making a Custom Field mandatory

[lindarussell]

I'm an HTML novice so I don't know how to do this!
I've created a Telephone Number field (user1) but peple filling in the form on the web page can get away with not completing it - if it isn't filled in no error is given.
I want the phone number to be mandatory because I want to make follow-up phone calls.
So how do I do it?  
Better still, I'd like to validate the field (i.e. minimum 11 digits) as well.

[DW]

In v1.87 of ListMail you can make custom fields required, but can't validate them for telephone number format (this might be coming later..)

What I recommend is using JavaScript.  I found a nice validation library which can accomodate phone numbers at the following URL:

http://www.virtualpromote.com/tools/javascript-regex/

Here's another one:

http://www.smartwebby.com/DHTML/phone_no_validation.asp

Regards, DW

[lindarussell]

Thanks for the prompt reply Dean!
I'll install the latest version and try out the suggested scripts.