There's no formula that you can use to blank out the cells (like
edit|clear|contents).
But you could use a formula that displays different things depending on what's
in that cell:
=if($a2="no","","Some other text or formula here")
If you're just trying to give the impression that those cells are empty, you may
want to look at Format|condtional formatting.
You can format the cell with a white font on white fill (or same color on same
color).