Have attached a sample database. When you click on the main switchboard - click on Batch. This opens the Batch form which is based on the Heat treat table. How can I modify the dropdowns in this form so that when Workorder 1 is selected - it offers in the combo box a list of all the workorders that relate to that workcentre? Then when the user moves to Workorder2, the dropdown they select will only reflect the workorders that are left e.g. if I have workcentre 123. That has 5 workorders: 10,11,12,13,14. When I choose 10 from this dropdown in workorder 1, the only choices that are left in workorder 2 are: 11,12,13,14. And when I go onto Workorder 3, the only choices I have left are what is left i.e. 12, 13, 14.