Help: Adding Property to Class that use IMPLEMENTS

[jude7]

Hi..
I have problem using class that use IMPLEMENTS. If i create a new class having interface from other class. The problem is I can't add a new public property or method in it. New property that i write didn't recognized by the instance object.

For example:
I have Interface Class called IHuman, have 3 Properties:
- Name
- DateBirth
- Sex
My Code for Interface Class IHuman:

Public Property Get Name as string
End Property
Public Property Let Name(Byval sData as string)
End Property
 
Public Property Get DateBirth as Date
End Property
Public Property Let DateBirth(Byval dData as Date)
End Property
 
Public Property Get Sex as Integer
End Property
Public Property Let Sex(Byval iData as integer)
End Property

Then I wrote another class called CEmploye that implements IHuman. Beside Name, DateBirth and Sex, i need new property named Salary.
My Code for Class CEmploye:

Implements IHuman
 
Public Property Get Salary as double
End Property
Public Property Let Salary(Byval uData as double)
End Property

My Form's code:

Private Sub Form_Load()
    Dim oEmp as IHuman
    Set oEmp as New CEmploye
 
    oEmp.Name = "Mike"
    oEmp.Sex=0
    oEmp.Salary = 1000   '<--error here
End Sub

Is there any solution(s) to add new method or property to this kind of class ?

Best Regards,
- jude -