We need a drupal expert to help us push the data from Focus(ERP System) to Active Campaign

Focus (ERP system) has the last purchased dates for the Customer accounts. They do not keep email addresses in Focus so we cannot do any import to AC(Active Campaign) with the native import tool. but Focus has the CUST ID and we can key off that in AC(Active Campaign). However, one CUST ID may apply to multiple contacts (so if 3 contacts are on file at a company then 3 contact records with the same custid). We need to write something that will bring a csv file into the server, key on the CUST ID, and populate a date field for the last purchase. then turn and push that last purchase data into AC.