The BUTTON keyword defines a button that will execute a macro.
The function must have the following parameters and visibility:
Public Function routinename(ByVal strPropName As String, ByVal lngDDID As Long, ByVal strPrevValue As String, ByVal strValue As String, ByRef varRet As Variant) As Long
▪strValue is current value.
▪varRet receives the value to be written to the property identified by the TARGETPROP keyword, which is optional.