I have a combo box on continuous subform I'd like to be dependent on a selection made in a combo box on the main form.

I've made a purchase order database. There's an order table, and order item table, a supplier table, and an item table. Each item is related to a supplier. When I make a purchase order, I select a supplier from a combo box on the main order form. I enter the order details (item and quantity) on the order item subform, which is a continuous form. For each record in the subform, I enter a quantity, and then from a combo box select the item being ordered.

When selecting the item being ordered, I'd like the values that appear in the combo box to be limited to items supplied by the supplier selected on the main form.