Hi,

I have a simple data structure to implement. I have 3 entities; Lecturer, Module and Allocation. A lecturer can have more than one module and a module can have more than one lecturer. This creates a many-to-many realtionship which I've resolved by creating an additional entity called Allocation. Lecturer has a unique key called Staff ID, Module has a unique key called Module Code and Allocation has a unique key which is a combination of both of the others i.e. StaffID and ModuleCode. I've creating 3 forms. Lecturer and Module are fine and I've prevented duplicate entries for StaffID and Module Code, but I don't know how to prevent a user for allocating a lecturer to a module more than once. i.e. how can I combine two fields and prevent duplicate entries for the combined entry?

Any help would be gratefully received as the resolution of a many to many entity relationship is fundamental to almost all of the data apps I need to build.

Thanks