go to main table form problem

If you want a field to be displayed on the form as a drop down and (go to main table form property)than make a table and a field and make a form and menuitem (display)and put that table in datasource
make an edt for that field and a relation to that table field.
make another table and drag that edt in that field.and in the target form put this table in datasource an drag that field in the design  grid.