Validate VAT number when leaving field

[Profillageret.dk]

Hello Guys,

I have a Prestashop 1.6.x system set up with one page checkout, and turned EU VAT validation on.
The way it works now, is that the field is validated when I press Accept Order and proceed to payment.
But I would like to validate the field when user leaves the field, because otherwise it will not remove VAT before payment.

 

Is that possible ??? 

 

Thanks.