I just did some similar work with Wavelab......I have Soundforge but never use it so I can't really help there.
Here's what I did. The peaks where I had crowd noise were much higher than any of the peaks during the music. So, I found what seemed to be the highest peaks during the music by checking peak levels throughout and normalized to that peak level. That way my crowd noise was no louder than the loudest music. Of course, I wanted to try to make it perfect so I went through and selected specific crowd noise sections and lowered the gain....but I wouldn't recomend that...it was a pain in the ass.