Adding custom fields in lists (like Expense Report)

How to add custom fields in the lists like Expense Report line items. I want to add Vendor name and their VAT number in the line item while claiming the expenses report.

Current extra fields adds to the overall expense report and not to the individual line items.

Also, is there any want to have first Supervisor approves and then Finance approves and the expenses are credited.

please help.

yesbee