proper way to split part then assemble?

OK, so I'm making a mold. I create a part, then split it intoseparate parts, then create an assembly out of the split parts toadd holes, dowels, etc.

If I add in or change a feature to the first part I have tore-split it for the changes to propagate. If I add in holes,dowels, etc in the assembly it doesn't propagate to the originalpart, but it will propagate to the split parts.

I'm just wondering if I can get everything to propagate after achange.

Is this something that I have to work with or am I going aboutsomething the wrong way?SolidworksAssemblies