In Sitecore you can use validation rules. By default there are three validations rules on each template:
- Is Integer
- Max Length 40
You can modify or add new rules in the sitecoresystemsettingsvalidationfield section in the content editor
With the use of an multilist you can set the rules for your template.
ATTENTION: Validation rules are already built in for version 5.3.1 but you can’t use them. Therefore you need to upgrade to version 5.3.2, which costs about an our. You can use regular expressions in version 5.3.1