Replace white background?

Photographed a family on white background. It was a new sheet so all the creases showed. In CO I can mask and adjust the white so as to blow it out and get rid of most of the creases. PITA!
Is there a way of masking and replacing the background? or changing the colour in CO?
or do I have to rely on photoshop...extra steps and all that.??

Would be great to add a layer with a "blend if" function, ala photoshop.

Thanks

Paul