This function indicates if the device does or does not exist using its Code property which is in the letter code and unit code format.
Description: This is the house/letter code and unit code of the device, such as "A1" or "q17".
Return value: status
Description: Returns -1 if the device does not exist, otherwise it returns the device reference ID number of the device. The reference number can then be used with the GetDeviceRef function.