Bus for only one Driver and vise versa

[alipezu]

I have 4 Tables
tblDrivers
tblBuses
tblSchools
tblSchoolTrips

I have database for a company Where there are 150 Drivers and Buses and 31 Schools.. Some Drivers have only one Trip in a School while Some have two
Trips in Two different schools with the same Bus they have in the first Trip..
I want only one Driver must have one Bus.. One Bus should not be Driven by more than one Driver and vise versa..
No Problem if each Driver has the same bus in Two different Schools..
I am attaching a Screenshot of my tables.. Please Help!!

[ranman256]

Then you will run a query to append a record to the tTrips table:

[busID],[DriverID],[SchoolID],[Date]