Isotype control for multiple CD antigens of interest - (Jul/29/2013 )

I am using multicolor flow cytometry. The number of CD markers of my interest are 6. All of my flow antibodies are IgG isotype from mouse. Can I use only one isotype control of same antibody isotype from same species (e.g., mouse IgG-PE) for multiple antibodies of same isotype and from same species ? Buying 6 isotype control is very expensive!!!

It's really expensive... But the problem is that they are all different colours. So if you use only mouse IgG-PE, this actually will tell you nothing about the "control fluorescence level" in the FITC or APC Channel. It only gives you the level for the PE staining. Another thing to consider is concentrations. The isotype control should be applied in the same amount as the antibody itself. But the main problem here really is the different colours. And using unstained controls, would that be an option ?