Header and Line

Hi Dear Developers
I have created a field in the header view of purchase order and line of the purchase order when i insert data in the header field I want to update the same field in line also based on the parameter form

Do you mean updating the field on purchTable should also updated it on lines? If so there exists a similar functionality.
AP → parameters → Updated → update order lines.
You have to add your field to HeaderToLineUpdate field group on PurchTable, so the same functionality will be extended to your field as well.

I added to that field group but when I chose the never option in the update order lines it is updating the field in purchLine

It should not update if the value is never. Try debugging the related code.