This looks that is something that could be done in Dynamic Drop downs instead of the DataAssist Search.
Although this will require that you have your tables in a certain structure which you might already have.
Otherwise to do this in DataAssist Search will require some custom coding. But you can create the first list to be a drop down list , and then have another record set that filters based on the first drop down list. so the user will make a select in the "sold not sold" drop down list and then they click the submit button which will then load the second drop down list.
This could be a lot of information, so let me know if you have any other questions.