Creating an IF statement within a Form

[csd003]

Hi, I am currently trying to create a form where I am able to check yes or no (start and stop in this situation) to categorize whether or not a person (in this situation a taxi cab driver) is using a certain cab number. The problem I am having is that I can't quite seem to find a way to make it where the cab driver can only be driving 1 cab at a time and that when i have "start" checked off next to their name, i can't place another "start" with their name and another cab number unless i check "stop" with the previous cab number which was assigned to them. Any ideas on how I should approach this? (Sorry fairly new to MS Access and don't know if i explained the situation correctly, let me know if i need to elaborate or re-explain something. Thanks!)

[pbaldy]

I'm not clear on how you're trying to design it, but I have actually designed this type of thing for cab companies. I create a drivers table, a cars table, and an activity table. That table has fields for the driver, car, start and end date/time fields (among others). Each time a driver/car go out is a new record in that table. That way I can tell who was in a given vehicle at any point in time (car 123 ran into somebody yesterday at 2pm; who was in it?).

[csd003]

I am designing it to keep track of permit numbers and from this form page, i'm planning on creating a report to know when a driver had a specific permit number and when they "started" and "stopped" using it. Basically to keep the information organized. The problem I'm having is that i don't know how to make it where if I give 1 driver a certain permit number, that no one can assign another number to them unless that number was checked off start.

[pbaldy]

Using the table I describe, you can search for records with that permit where the end time is Null (using DCount() or a recordset)