Validation of Customer Tax Registration Number

Dear,

When entering a customer and under the account site go to "Tax Profile" to enter the customer Tax Registration Number, how can we make the system validate that the number (including country code) is correct and corresponds to the country entered for the specific customer?

I've seen there is some kind of validation for e.g. Netherlands for the field "Default Reporting Registration Number" in the section 'Tax Registration', but not for the field "Tax Registration Number" in the lower section 'Customer Account Site Business Purpose Tax Details'.

Any idea about how to solve this?

Thanks!

// Lars