You can't change the error output from a property node from within the facade since the facade only gets called after the property VI has run and modified the contents of the display state information. If possible try to catch invalid values in the property VI itsefl. If there are errors that the xcontrol will need to report you will need to provide a separate mechanism.
Something that I have used in the past to good effect is the idea of an error stack. The error stack itself is an array of error clusters that resides in the display state data and is maintained as a circular buffer by the xcontrol code. To access this value from the calling program create a read-only property that reads the contents of the buffer and then clears it.
Mike...
