The description of your problem is rather unclear. That said, setting a breakpoint inside the general
mouse event handler may have been a very bad idea (if that is what you did?). IIRC it catches all mouse event, including mouse movement - as a result you'll pretty much keep getting events as long as your hand touches the mouse (unless you're keeping it very still...)
Instead, always set the breakpoints inside the specific
handlers, e. g. ButtonUp, or ButtonPress.
Also, you could try to use [F5] to start or continue debugging instead of using the mouse to click the toolbar button: if you don't touch the mouse, then chances are high you won't immediately cause another mouse event, triggering a breakpoint.
When you said 'the interface always lie in top-most, I suspect you mean Visual Studio? If you hit a breakpoint, it will always be brought to the top, so that's normal. You then said 'the procedure has no response'. I didn't understand that at first, but if you refer to your own program, then this is normal, too: The moment your program hits a breakpoint, it is interrupted and will not respond to any interaction! Remember that processing user interaction is part of your program, and if you pause it with a breakpoint, then this processing will be paused, too. You can always press [F5] or click the corresponding button on the toolbar to continue exection of your application.