Hi
If you have small set of data then you can use drop down becaue dropdown data will be loaded run time.
For OVS you can execute query (QueryByElements of ovs BO) at run time and get records. You can also use parameter in query to filter results in OVS list and pass selected value back to your field.
If you dont want to use only dropdown then you have set your field property CCTS type = code
and you have create a dummy datalist with field name and value for droplist then have to fill this datalist with query(similar to OVS) this will be a tricky but drop down is achievable.
Regards
Sunil