Here is an example:
Mainform
Start Date is 14.11.2017
End Date is 17.11.2017
No.of Overnights is 3 nights.
Is that possible to auto create 3 subform (based No.of Overnights).
First one "Date (Overnight)" is 14.11.2017 (the same as "Start Date")
Second one "Date (Overnight)" is 15.11.2017
Third one "Date (Overnight)" is 16.11.2017
Please check the below photo.