tsql test script

I need a tsql script to generate some test data 1. for each row in a table, read the companyid and customer name 2. for each company generate a 7 column transaction for each first of the month between the start date and the end date (current month) 3. test if transaction exists in a second table and if not, insert it a transaction would look like [CompanyID] read name from first table ,[TransID] NULL ,[TransType] 'Maintenance' ,[InvoiceNumber] NULL ,[Customer] read name from first table ,[SettlementDate] 1/1/2017 ( and every first of the month until current month ,[Amount] 99