How to restrict the value of value set on the form?

   Hi Experts,

If we make a value set in which value are 1,2,3,4 & so on......... Then attach that value on the Dff . After that when we call that value of value set on the Form Line then that particular no which is already called can not be called again for another line. Is it possible through personalization?

As we want a no on the Purchase Order Form line so that we can assign a different no: to the PO lines for some particular Items.

Thanks in Advance