implements interfaces in VBA

[raven000]

Hi,
I am using MS Excel and Im trying to write a macro(VBA) that would use classes and implement an interface. I have no idea what im doing wrong but i keeping getting an error prompting me that the Object module needs to implement a function that the interface has declared. But strangely the function is already implemented. My code is a follows:

clsInterface

Public Property Get LibraryItem_CheckedOut() As Boolean
End Property

clsDerived

Implements clsInterface
 
Public Sub Class_Initialize()
    MsgBox "in derived"
End Sub
 
Public Property Get LibraryItem_CheckedOut() As Boolean
    MsgBox "in derived"
End Property

And finally, ThisWorkbook

Dim cls As clsInterface
    Dim derived As clsDerived
    
    Set cls = New clsInterface
    Set derived = new clsDerived
    Set cls = derived

Ive wrecked my brains of this for hours and have not figured out why i get the error. Again, the error is: "Object module needs to implement 'LibraryItem_CheckedOut' for interface clsInterface

Thanks a million
raven