You post isn't real clear (e.g. = to End_date-Start_date). Something is equal to end date minus start date? End date to start date? And what equals those/that?
If end minus start gives you some record count (e.g. 6 days = 6 records needed) then I think you'll have to create a loop with that result as your counter, then add a record to a DAO recordset you created based on the form recordsource by appending to at least one field for each loop. When done, you requery the form.
Not sure if I understand the requirements so that's my take for now.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.