SOLVED Get Message from TreeView gui dialog

I'm writing Command Data plug-in and have a TreeView custom gui element where user can drop some things to create elements tree.
Now i need to send, for example, Tree items count to main GeDialog window each time when user interacts with TreeView.
How i can make it?
I was found this tread, where using SendParentMessage, but it's not working with TreeView.

Hello,

SendParentMessage() is a member function of GeUserArea. It is only relevant if you create a custom GUI element based on GeUserArea.

A class based on TreeViewFunctions is used to define the behaviour of a TreeViewGUI. It is not based on GeUserArea.

In TreeViewFunctions, you could inform the host GeDialog about an event by sending a custom core message using SpecialEventAdd(). The GeDialog can catch this message with CoreMessage(). If you want to send data, one way is to store the data in a global variable which is then accessed by the dialog.

best wishes,
Sebastian