Originally Posted by macropod

For the BH4, you could use a field coded as:
{EQ \s(\f(,4))}
with the 4 subscripted.

Note: The field brace pairs (i.e. '{ }') for the above example are all created in the document itself, via Ctrl-F9 (Cmd-F9 on a Mac); you can't simply type them or copy & paste them from this message. Nor is it practical to create the field via the standard Insert|Quick Parts|Field dialogue because of the need to subscript the 4.