websphere MQ Adapter segmented messages

I need to get segmented messages from an MQ queue. The original message is too big so the sending application is segmenting the message. I need to get the segments and re-assamble the message. According to the websphere MQ adapter manual I have to create an adapter service to get segment by segment using the offset property.
I talked to the MQ admin and he told me that I just need to use the message flag equal to MQGMO_COMPLETE_MSG and the MQ manager will assemble the message, but I don’t see that opton on the adapter GET service and the manual does not mention anything like that.
Any recommendaton about how to re-assemble the segmented MQ message?
Thanks in advance.