Upper limit for exposure in Auto Levels tool?

I am digitizing my slide-collection by taking pictures of the slides within the slide projector. So I get several hundreds pictures very fast and I expose it using profiles which I have defined and stored. These profiles are using the Auto Levels tool and I am astonished about the resulting quality of digital pictures of the old slides.
But some of the pictures are rather dark (e.g. twilight hour) and the auto level tool corrects it: the exposure values increase to very high values (e.g. +6 EV). Now my question: is there a possibility to set a limit to the automatic exposure in the Auto Levels tool (e.g. max exposure = 1.5 EV)?

Auto Levels fails on such shots and currently there is no workaround.