You can use the nodemap to retrieve the value. I think CVB comes with a few tutorials that use the nodemap to access camera properties. For instance there is the VCGenICamGrabConsoleExample in %CVB%Tutorial\Hardware\GenICam\VC\VCGenICamGrabConsoleExample. There, have a look at the method void genicam_access(IMG hCamera). In this method, the camera parameter “Width” is queried. You can do the same for the exposure time.
Also, there are a few threads regarding nodemaps that might be worth checking out.