Display a dropdown IF another cell has a specific value

[Adendum]

Hi Gurus,

I would like to be able to display a dropdown of data validated options using a formula, some thing like =IF(E3="No","dropdown","n/a").

But I can't workout how to replace "dropdown" in the formula to get a data list and display it as a dropdown.

So if E3 is changed to yes we see the text "n/a" but if E3 is set to "Yes" we get a dropdown list of options.

Is that possible?