Please note: I do not endorse the mousewheel technique or use it at all and it can be problematic (with upsizing as well as making sure the *.dll is accessable.)

I only posted this example to show that there is a better, simplier way versus using the mousewheel technique.

To prevent a user from utilizing the middle scroll wheel and accidently scrolling to the next record....

1. Make sure you are returning only the requested record to the form (ie. don't have the form return all records but use criteria to return a single record.) This not only makes your form function better but also allows for #2 below.

2. In the OnCurrent event of the form, simply add this line of code:
Docmd.gotorecord,,acfirst

If you need to add a new record, the docmd.gotorecord,,acnewrec won't work with above. I personally create a new record via vba coding (writing in the DateEntered and EnteredBy or required values) and then again, open that single record as #1 above states.

If the user then tries to scroll, it will automatically go to the first record (which is the 1 record returned to the form.)