multi-threading

In my gui, i need to perform two task simultaneous.One is send a file via serial port communication and other is display the status of communication on GUI as static text .Both done in a single button control.For this whether i need to create separate thread?
I try this without threading.First i send the some fixed size of file and then show the status and continue the same for full file size.But when i open other application like calculator,the status display going hangs.but the file transfer is progressed.

Help required

You should use additional thread(s) for serial communications. The best way (IMHO) would be using overlapped IO wirh a worker thread processing serial Input (read) and UI thread (with a message pump) processing serial Output (write)
See the example in Serial Port I/O