I, personally, have not heard of this one yet. Maybe you mean 'Floor',
'Ceiling', 'Lower', or 'Upper'. Check the help menu for the details on
these. Maybe you are referring to a user defined function. If this is the
case you will have to provide a lot more details and, most likely, post your
question to the 'Excel Programming' discussion group.
If you have a list of net cap categories, and one of them is zero, you
can use a lookup formula or INDEX/MATCH combination to return the cap
multiple for a particular capital measure. I don't know that there is
a single zero-cap calculation for a generic scenario, but anything
like net debit cap, bond rating, and similar risk calculations can be
accomplished by using lookup tables.