Once you move to a "new" record in the form, the record is not written to
the table until you make a change and then move away from it. You can fix
the problem with the last tab key by changing the Cycle property of the form
(on the Other tab of the form's Properties window) to Current Record instead
of All Records. That won't solve the problem with the mouse scroll wheel,
however.

There is a utility available to disable the mouse scroll wheel, although I
don't have the link to it handy. Do a search of this newsgroup for "mouse
scroll wheel" and you'll probably find it. One note: I believe this
functionality has changed under Access 2007, where the scroll wheel no
longer does that by default.

Carl Rapson