keeping clients from editing custom fields

[ACPS]

How can I keep my customers from editing information within a custom client field.

 

Example...each client is issued an account number but I want to prevent them from changing it. I need to have it showing in the client area, just not editable.

 

I tried hiding it in the clientareadetails.tpl using the the line below but it didn't work.

 

<input type="hidden" name="accountnumber" value="{$client_custom_field_accountnumber}">

 

Anybody have any suggestions?

 

Thanks