How long is ridiculously long?  If this is associated with your population
of combobox issues, are the number of entries too long for the method that I
suggested?  If so, there are probably too many selections for your users to
handle, let alone Word and you should try and split the number of items into
more categories and have the user first pick a category, then and item from
that category and then a sub-item from the item that they have picked in the
category.

For the guy whom I was helping in the link to which I directed you, a
modification of that method was use to deal with 4 or 5 levels of selection,
though, not because of the total number of items, but because of the desire
to categorise them at a number of levels.