PROPERTY SET not defined for: <property name>

You tried to assign a value to a property, but did not define a Property Set procedure for the property. For example:

Dim myInt As Integer
Property Get MyProp As Integer
   MyProp% = myInt%
End Property
MyProp% = 3       ' Illegal because there is no 
                  ' Property Set MyProp defined 

Define a Property Set procedure for the property to which you want to assign a value.