Arduino GUI Com-PortI

Hello everyone it's me again...

So I've created a GUI (attached) and with the Panel inside the GUI I want to connect my Arduino Mega with a Com-Port(USB) of my Laptop. I want to be free which Com-Port I have to use in the end, I don't want to use always COM4 for example maybe it'll be COm5 or 6 for example depends on which Laptop or Desktop I#m running my GUI.

if i press the button connect the GUI or programm should connect to my Arduino Mega and show me on which Port it is connected in my Edit Text above. If I press Disconnect it should disconnect of course?

Is there a simple way to do this? If yes how ?

I'm thankful for any help