VBA - Excel 2007 Removing Values

Hello,

I am working with excel right now with their data validation feature.

I have a yes no option in cell A3.
In cell A4 I also have a dropdown selection.
What I want to be able to do is when A3 = "No" I want the Data validation dropdown for A4 to = "" (Blank).

I have added a default button in for the overall sheet, so by default A3 is yes and A4 has a value, but if the person selects no for A3 I want A4 to automatically go blank as the row is hidden when No is selected, and I don't want a value to be calculated for A4 at the end of my sheet.

I am not sure how to code this. Any help would be greatly appreciated!

-Bob