Hello all, I'm using a VAR_SIZE message box in RTX-166. Most of my messages are short, only 2 bytes, but some are longer at 46 bytes. Reading through the manual it says that variable length messages require two additional bytes of memory space to store the message length - fair enough. Q. How can I determine what type of message is returned from a call to os_wait_message i.e. in my case determine whether the message is 2 bytes or 46 bytes long? I would have liked to have done a simple check on the received message size but I can't see how this is achieved. Will I have to create my own type/length field in each message or can the os provide this information for me (it stores the message length anyway!?) Any advice would be appreciated. Thanks Paul