Macro to provide list of alternatives based on cell value

Hi,

I am trying to provide a drop down list of alternatives from another worksheet based on a cell value. I have attached a basic workbook to explain further.
I have created a form into which a user must enter a postal code. This postal code may have a number of different alternatives:,
eg: Postal code 4000 may belong to the following areas: Perth,Perth West,South Perth,North Perth.

What I would like to do is present the user with the 4 alternatives so that they can choose the correct area. I am thinking that I will need a macro to do this. If anyone has any suggestions it would be most welcome.

Thank you for your help.

Wayne