I am using Solidworks 2018 Student Edition and I have a question about making parts partially independent.

I have a part and want to alter a number of it's dimensions once the part is in an assembly without these changes effecting the other instances of this part in the assembly and I don't want to make each part independent. Furthermore the dimensions need to be controlled by the assembly. I can't currently see away of achieving this and want to ask if anyone knows if the parts could vary in the assembly without making them independent.

To give more context, I have a part (call it Part A) that I wish to use a large number of times in an assembly. Part A is composed of 1 to 4 repetitions of another part (call it Part B). Part B has 3 dimensions that need to be able to varied, each repetition in a Part A differs from the other repetitions and how these instances of Part B differ will also differ for each Part A. For each Part B these 3 dimensions also need to be controlled by constrains and geometry in the assembly that Part A is being placed in.

I've been able to create Part A and create configurations that allow me to control the number of instance of Part B in an instance of Part A, but when I place part A in an assembly and constraint the sketch of one of it's Part Bs to the assembly's geometry the changes to Part B are shared across all instances of Part B.

Thus far I've resorted to making all instance of Part B independent but this is a headache as any change to the dimensions or geometry of Part B has to be repeated for every Part B instance used in the final assembly. I feel there must be a way to be able to differ the 3 variable dimensions without resorting to making every Part B completely independent, but I cannot seem to find it.

I might have a more fundamental problem with my approach. If anyone knows if this semi-independence can be achieved and if so how, it would be a great help.