SubAssembly Configuration

It seems that after several years of using Solidworks, still I need some advice on assembly configuration.

I need an assembly with several configuration. Later this assembly will be used as a sub assembly with different configurations in another assembly.

I've tried 2 methods and I'm facing some troubles.

First Method I used:(test1.SLDASM  & Assem1.SLDASM)

I created the assembly and added several global variables, added two configuration and changed the variables for each configuration.

Result : The assembly works perfectly and all configurations show as they're supposed to (when opened as a stand alone assembly)

Problem: When two instances of this assembly is used in another assembly, I can't have separate configurations for each instance.

I have to keep the same configuration for all instances.

Second Method I used:(test2.SLDASM  & Assem2.SLDASM)

I created the assembly and added several global variables, added a design table and configured global variables in the design table.

Result : The assembly works perfectly and all configurations show as they're supposed to (when opened as a stand alone assembly)

Problem: When two instances of this assembly is used in another assembly, changing the configuration of one instance, changes the configuration of all instances.

How can I use this  assemblies as a sub-assembly with different configurations?

Any kind of help/advice is much appreciated.