Match Two Cells And Subtract

My workbook has 3 worksheets in it, Data Entry - Components – Jobs. The first worksheet contains 2 buttons to enter new data via user forms. The second worksheet has 3 columns in it, component code, date, quantity and they are populated via a user form. The third worksheet has 4 columns, component code, date, quantity and Job number and it is also populated via a user form. When a person enters the data into the job user form and then clicks the command button to add it to the spreadsheet I need it to also find the matching code in the component worksheet and subtract the job quantity from the component quantity. So if the component worksheet has Envelope1 with a quantity of 25,000 pieces and I enter a job that used 10,000 of Envelopel1 the component worksheet would be updated and only list 15,000 pieces.