You will need to create a custom combo class.
RowSource = country.name,code
BoundColumn = 2
ColumnWidths = 50,0
ColumnLines = .F.

This will create a combo that will show the country names in the list but store the contrry code

Add this combo to the grid instead to the standard combo. If you only want the user to see the country names and not the codes you will need to set the column's Sparse property to .F.

When you change the selection in the combo the county field in the grid's table will be changed to the code from the combo

Best regards

Andrew