Fetch contents of a field on to a text field on a form.

I need some little help in ax 09.

I want to display Vendor contact details on the PurchTable form.
I have added a new field (VPhone with an Extended DataType of Phone) on the PurchTable Table and drag droped the field on the PurchTable form.
I want when a new PO is created, the vendor information to automatically load on the form and my new field to load the Vendor Telephone Number.

Any help please…