IF i WANT TO DIVIDE A NUMERATOR BY ONLY THE NUMBER OF CELLS THAT HAVE AN ENTRY (WHICH CAN VARY), HOW WOULD I DO THAT?
Supposing that the entry is 10 and the numerator is 20, you can do that using the formula below.
This places a slightly different interpretation on your question. If the data entries lie within a defined Range 'Entries' then
= Numerator / COUNTA(Entries)
would do what you state.
If it were that the range is fully populated but might grow as data is appended then by placing it within a Table the range becomes dynamic. In that case the formula would be
= Numerator / ROWS(Entries)