Your error trapping only catches the subnet registry read. This would trap both.

code:
 $DefaultGateway = ReadValue("HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\El90x1\Parameters\Tcpip", "DefaultGateway")
If @ERROR = 0
	$SubnetMask = ReadValue("HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\El90x1\Parameters\Tcpip", "SubnetMask")
	If @ERROR = 0
		If $DefaultGateway = "169.112.1.1" AND $SubnetMask = "255.255.255.0"
			? "Default Gateway: $DefaultGateway"
			? "SubnetMask: $SubnetMask"
		EndIf
	EndIf
EndIf