crm vtiger modify and make arrangements

need to make some changes in vtiger crm. Numbering in Invoices Module need to work with 2 types of invoices invoice example where A and B bill for selection according to the type of customer, the invoice must select A or B with a separate invoice and correlative numbering [login to view URL] 2nd Purchase Order with custom field COST PRICE WITHOUT VAT [login to view URL] First page of the forum: description and code Second page of the forum: correction) Page 3rd Forum application to version 5.4) this is for the PURCHASE ORDER Provider is generated with the new field of COST PRICE WITHOUT VAT from any entity in which a purchase order is generated ...