Text History Window

I'm making a program to keep incoming calls organized. Sort of like for a secretary to keep a record of who calls in and who they wish to speak to, etc. I wanted to make a history window that exports the information from the main page to a secondary window to keep track of all the notes during the day. The export functions properly. Resetting the form clears the data and pastes it onto the other window. The only problem is that when the window is opened the first time, it displays all the information accurately, but once the history window is closed, all data in the textbox is erased.

Is there a way to keep the info in the textbox even after closing the window. (Note: The main page of the program remains open during the entire process. Only the history window is opened and closed.)