Discern a value from Two Columns in VBA

I'm sure this has been asked before, and I have searched every avenue high and low before asking.
I have two columns that contain text number representing times, for my purpose I don't really need to change them to actual times, column A contains a start time and column B and end time, i am trying (and failing in VBA) to discern what would be an Early, Late or Night shift. Early commencing 600 (06:00) to 1059 (10:59), Night finishing after 300 (03:00) to 0800 (08:00). Shifts are no more than 12 actual hours in length and will result in either and E, L or N in another column as a result (no formula). Late runs between 1100 to 259, and not all shifts are full lengths (my problem).
what I need is VBA that will do the comparison between two columns in a single pass (I seem to currently be running four loops in my tests, which provide a result, but are quite variable.

Can someone please prod me in the right direction