[Dev-C++] how to update data constantly?

My whole projects have two thread.
one thread is reading RS-232 communication port.
another thread is Win32 GUI to display the data got from RS-232
communication port.

The design I had is:
Buttons on Win32 GUI.
So when the button is clicked, the corresponding data is read from RS232
thread, and display in the GUI thread.

BUT I want to have a constantly updated display.  That is, there is NO
button to trigger the data update.
When the data of RS232 thread is updated, my display of GUI thread need to
be updated.
What should I design?

My consideration for the design is:
add a constant interval timer to trigger the data update.
but how to implement it?
and do you have any other good idea?