I created a field in the purchorder form called externalCategoryId. It will display the list of category id from the master. And there is already an AX Category id appearing in the purchase order form for each PO. There is master set up where the AX categoryId and the ExternalCategory Id are mapped in a screen. In the purchase order form ,when the user selects the PO and selects the AX categoryId ,automatically in the externalCategoryId should show the mapped Id from the set up screen. And if user wants to retain that value then he should be able to save it.
Actually I tried by writing a display method to appear the extCAtegoryId pertaining to AX categoryId. But in the field properties I could not declare that method because I have to declare the table and field name so that it saves in that table. Please let me know how can I make it to appear and then save the same. Please let me know if my explanation is not clear.