uncheck compilations in new itunes

I have a CD with various artist and tons of songs. I want them to be compiled on my ipod. In the CD there is a mix of songs that have the "part of a compilation" box checked but others do not. When I try to change it for the entire album I cannot check or uncheck the "part of compilation" box. It shows a "-" instead of a check mark. Is there a way that I can make them all checked or unchecked without having to go through each one individually and making them match? When they all match, like in other albums, the check mark is there where it is supposed to be but if there is a mix the check mark disappears and is replaced by a dash - and it does not let me check or uncheck it. I need help to see if there is a way to change this without having to go one by one.

Thanks