In Debugging, I want to debug only the active form

I have problem in the debugging process. The problem is that when I debug the active form (Opening aspx form) by going to Debug menu -> Start Debugging, all the project forms are debugged, even its not related at all with the active form I want to debug. If any of these other forms have error, the debugger shown the error and my form is not reached and not show, Thus, How can I restrict the debugging process to only the opening active form?
Thanks
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