Check out this post. A custom form is nothing more than a regular detail screen with entry components that update a row in real time…and then a button to add those values to another table. It gives us a lot more freedom for validation.
I also mention a technique to make a custom form reusable from multiple different screens in the same app. That’s only if you need to reuse the form in multiple places.
Just be aware that the use of a custom form will count against your edit/update counts a lot more than a native form would.