Returns the number of messages currently kept in the frame's message history. If accessID is nil, this number reflects the number of messages which can be seen by scrolling the frame, including (but not limited to) the list of messages currently displayed.
If accessID is specified, this number reflects the number of messages with that accessID that can be retrieved by using
accessID- accessID for the type of message you want to count. (
count- Number of messages currently kept in the frame's message history (