Forgive me if I've misunderstood you, but when you create/edit a relationship in the relationship window, you are presented with a dialog box that allows you to set referential integrity.
Not sure about graphics or Active X labels but for native Access controls you can set the "ControlTip Text" property of the control using the Other tab of the property sheet.
If you look at the backend db you posted, you will see that none of the tables has a PK. Anyway, since you have marked the thread as solved it's a moot point.
I don't think my original suggestion gave the desired results when the time was 03:00 am
Don't understand why you are making comments on the use of Now() function. I haven't used it:unsure:
I've looked at this again. The following works for me:
=IIf(Hour([BusinessDatetime])*60+Minute([BusinessDatetime])<=180,[BusinessDatetime],[BusinessDatetime]+1)