Of course you could just close the preview window everytime after you're done, but wouldn't it be nice if Cinema did that for you? To do that I wrote a little script. It currently only works on a mac because I'm using apple script to close Quicktime but I think something similar is possible on a PC. The only unresolved issue is, that I have to put the closeQT.app in the root directory of Cinema 4D (in the MAXON folder), which I feel is rather "unclean".
The (extremely basic) scribt goes like this:
var filename = GeGetStartupPath();
filename->SetLastString("closeQT.app"); // closeQT.app is the compiled apple script
The apple script is:
tell application "Quicktime Player"
Now every time you start a preview the script first closes quicktime ant then starts the new preview.
If you have improvements for the script or a way to adapt this for a PC please feel free to post them.
My ideal way of this working would be as compiled .cob in a subfolder in the plugins directory, where according to the os (checked with GeGetCurrentOS()) the appropriate application for closing qt is called from within that subdirectory. I tried GeGetRootFilename() but it somehow didn't give me a useful path to the closeQT.app.