Vary transformer core stack depth and change shell positions

[john_wilkinson3]

I have drawn a specific electronic transformer, see attached.

It has 2 end bells and between the end bells is a lump of steel that represents the core.

In the instance attached the core has a thickness (stack) of 1.25"

I would like to be able to change the stack to 1.5", 1.75" and 2", and for each case the shells move appropriately.

I am sure this is so simple but I am new to mechanical CAD and would like a step by step approach so I can reproduce it.

Many thanks,

John