All you need to do is make another sub like ModifyIcon or whatever you want and copy exactly what is in form load except for

Shell_NotifyIcon NIM_ADD, tTrayIcon

and change it to

Shell_NotifyIcon NIM_MODIFY, tTrayIcon

also make sure to add Const NIM_MODIFY = &H1 in your declarations, you can change whatever you want with the icon in the modifyicon sub, good luck