You can do this with an event macro.

Assume the primary drop down list is in cell A2 and the dependent list is in
B2.

Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
Application.EnableEvents = False
On Error GoTo sub_exit
If Target.Address = "$A$2" Then
Range("B2").ClearContents
End If
sub_exit:
Application.EnableEvents = True
End Sub

To use this:
Select the sheet where you want this to happen
Right click the sheet tab and select View code
Copy/paste the code above into the window that opens
Close the window to return to Excel

--
Biff
Microsoft Excel MVP


"Roady" wrote in message
...
Hello:
I currently have two columns:
Column A is Countries
Column B is Cities associated with those countries in Column A

I have the data validation set up so that when you select Australia, for
example, in Column A, it limits/narrows the drop down list in Column B to
only show choices of cities in Australia (Sydney, Brisbane, etc.).

Here's my problem: when I have already selected the Country and city
(Australia and Sydney for example) and then later decide to change the
Country choice, it still shows the old city that I chose for Australia.
So, I
may change the country to Japan, but it will still show Sydney in Column B
unless I click on the Column B drop down.

In order to avoid careless mistakes, I would like to have it automatically
trigger the Column B to go blank if Column A is changed. Thus prompting
the
person to know that they have to fill a choice in for city from the Column
B
drop down.
Is this possible?

Much thanks!!
JR