Binning and VPhot

Sometimes I take 10-12 images of a faint variable in order to stack. However, I frequently have an NSV or ASA variable in the same field that is bright. My practice is analyze each image with a bright variable and then bin the results. However, I seem only to have an option for binning 5 images. So, for example, with 12 images I turn up with 2 bins of 5 and 1 bin of 2. Is there a way to change this so that I can specify the number of binned images?

Ed