This is what I do: in thisform.error I add the following code.

LPARAMETERS nError, cMethod, nLine
IF m.nerror=1429
	thisform.omessage.warning(PROPER('invalid communications port error, '+;
		'ensure that the port specified in the gage setup is valid and '+;
		'available. you will need to close any programs that may have it open.'))
else
	RETURN DODEFAULT(m.nError, m.cMethod, m.nLine)
endif

omessage is just part of my framework (codemine) that displays an error box.