Make a merged cell bank (independent) when drop down list changes to a specific value ?

Hi all,
I am a newbie of Excel and am struggling with drop down list. The problem is:
- I have a drop down list on B3 which contains, let's say, PIG and CAT.
- I have a independent merge cell from D5 to D10 , called "SKY"
- When CAT value is selected, people can fill all informations in SKY cell.
- Then I want to change to PIG, and I would like all the information which I have filled before becoming blank, so that I can fill new information in SKY cell for PIG.

Private Sub Workbook_SheetSelectionChange(ByVal Sh As Object, ByVal Target As Range)

Select Case Range("B3")
Case "PIG"
Range("SKY").value = ""


End Sub

I have tried it with the code below but it doesn't work. It clears the content but it is able to fill a new information.
Anyone help me could be appreciated.
Thanks a lot