how to mirror a specific distance?

Hi,

I have an assembly that I would like to mirror, then save the mirror assembly as a master assembly so any changes I make to the first will be mirrored in the second.  I am also having trouble mirroring the components a certain distance apart.  I go through mirror components wizard in the linear components menu, but I cannot figure out how to do it so the parts lie a specified distance from each other.  Thanks in advance for your help!

Hinton

SolidworksAssemblies