PO Number Sequnece (Can we append Vendor Account toPurchId field)

Hi All,

1.Can any one tell me from which classes the PurchID number sequence is generating??

For Ex: PO-1122 and i am selecting VendorAccount(OrderAccount)  can i append this vendor account to PurchId field

is it possible ??

like i need PO Number PO-1122V6789 here PO-1122 is PurchId, V6789 is Vendor account Number.

Thanks,

Krishna