JHH-
Just FYI...posting this question in the Vision forum would probably get you more responses.
I haven't found a ready made example program for CVI to do this (although there is one for LabVIEW), but it shouldn't be too difficult.
Try using the imaqGetLine function - it will return a line of color pixel values, and then you can perform use the imaqColorHistogram,etc on that.
Hope this helps-
Julie