You would likely need to add another field to your DB that you would update or see if it was updated so you exclude those items during the initial query but adding to your query that that field is Null or contains a date, et (Not knowing what else is happening to your DB table).

If you have control over the DB table, in your current process you would add an Update DB and through a loop have it update that fields that you are going to use in your form start to with "In Progess". When your Invoked Form Process was completed you would have another workflow that would set the values to "Completed".

Just some thoughts