Hanging Punctuation


In the course of developing a revival of Mergenthaler Linotype's Benedictine (1915-1922), I am considering the possibility of including hanging punctuation marks (quotes, periods, colons, hyphens and the like) in the OpenType implementation. I was thinking of using contextual alternates to substitute punctuation marks at the begining/ending of lines with the corresponding hanging (null-width) marks. However, I haven't been able to figure out how to detect within the "calt" feature a begin/end of line event. Is this possible? Or, more generally, is there any way of implementing mechanically this type of substitutions?

Thanks in advance for your advice.