Please help!
I have students and demonstrators (demis), working on different days in different labs and different benches. Each demi can have multiple students. I need to link each student to his demi, based on the day, lab and bench. I want [student details].[demiID] to be filled in automatically with the correct value from [demi details].[demiID]. I tried to build nested iif expressions (iif([prac day]=1 and [prac lab]=1 and [prac bench]=1,1,null) etc) in [student details].[demiID] to generate the matching value (1 - 40), but by the 12th case (out of 40) it is "too complicated" according to Access.