I have a cell that has data validation, forcing the user to choose from a
drop down list. As it is now, the user must scroll down through the list and
choose the appropriate bit of data, or they can type the full data in as long
as what they type matches the list. What I have been asked to do is make it
so when the user begins typing, the matching data would begin to appear in
full.

Let me explain a little better. The validation list contains the names of
over 50 sites.
what I want to happen is when the characters "AL" are typed the cell begins
to fill in either "ALAN ROAD" or "ALTON DRIVE". The user can then continue to
type or select either site. This is strictly a choose only cell, it does not
modify the list in any way. I hope this makes sense.