Drop Down List Issue

I posted this under general excel and they suggested that I post it here (stated that it would require code)....

I'm having a problem with my drop-down lists (I hope I can explain it sufficiently).... Simple example:

In D10 I have a drop-down list created through data validation. One of the options is blank and the others are Yes No, Numeric, Multiple Choice)

In D13 I have another drop-down list that is created through data validation based on the option picked in D10. (if you pick Yes No you get the options Ask until Yes, Ask until No. If you pick Numeric you get the options Ask Always, Ask Until Valid, Ask only Once)

Here is an example of my problem. If you pick Yes No in D10 and then pick Ask until Yes (D13) and then go back up to D10 and pick Numeric, D13 remains Ask Until Yes. I want D13 to change to blank until an option is picked from the drop down box.

Any help you can give me is appreciated!