Password validations in OVF XML

Hi

I am using a static OVF property of type 'password' in my virtual appliance.

Though we have an option to validate the password length using MinLength/Maxlength, I am not sure how to do more complex/custom validations.

For instance, is it possible to validate based on custom criteria such as following?

- Enforce at least one numeric or alphabet

- Allow certain special characters but not others

Are there any other ways this could be achieved?

Thanks

Sabareeswar