dynamically binding data to a combobox in datagridview

Question

I have a datagridview which is bound to a databindingsource one of the column in this datagridview is a combobox the combobox is also bound to a different binding source now my requirement is that once an item from the the combobox is entered into a row that item should not be shown in the combobox later. for eg. i have doctor,engineer,advocate in my combobox so when i enter the first row all items are displayed and in the first row i have selected doctor from the combobox. now when i enter the second row of the grid the combobox should only have engineer and advocate and viceversa